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3090-3093
The bridge then is balanced, and from the balance condition the value of the unknown resistance R4 is given by, 2 4 3 1 R R =R R [3 64(b)] A practical device using this principle is called the meter bridge Example 3 7 The four arms of a Wheatstone bridge (Fig
1
3091-3094
64(b)] A practical device using this principle is called the meter bridge Example 3 7 The four arms of a Wheatstone bridge (Fig 3
1
3092-3095
Example 3 7 The four arms of a Wheatstone bridge (Fig 3 19) have the following resistances: AB = 100W, BC = 10W, CD = 5W, and DA = 60W
1
3093-3096
7 The four arms of a Wheatstone bridge (Fig 3 19) have the following resistances: AB = 100W, BC = 10W, CD = 5W, and DA = 60W FIGURE 3
1
3094-3097
3 19) have the following resistances: AB = 100W, BC = 10W, CD = 5W, and DA = 60W FIGURE 3 19 Rationalised 2023-24 Physics 102 EXAMPLE 3
1
3095-3098
19) have the following resistances: AB = 100W, BC = 10W, CD = 5W, and DA = 60W FIGURE 3 19 Rationalised 2023-24 Physics 102 EXAMPLE 3 7 A galvanometer of 15W resistance is connected across BD
1
3096-3099
FIGURE 3 19 Rationalised 2023-24 Physics 102 EXAMPLE 3 7 A galvanometer of 15W resistance is connected across BD Calculate the current through the galvanometer when a potential difference of 10 V is maintained across AC
1
3097-3100
19 Rationalised 2023-24 Physics 102 EXAMPLE 3 7 A galvanometer of 15W resistance is connected across BD Calculate the current through the galvanometer when a potential difference of 10 V is maintained across AC Solution Considering the mesh BADB, we have 100I1 + 15Ig – 60I2 = 0 or 20I1 + 3Ig – 12I2= 0 [3
1
3098-3101
7 A galvanometer of 15W resistance is connected across BD Calculate the current through the galvanometer when a potential difference of 10 V is maintained across AC Solution Considering the mesh BADB, we have 100I1 + 15Ig – 60I2 = 0 or 20I1 + 3Ig – 12I2= 0 [3 65(a)] Considering the mesh BCDB, we have 10 (I1 – Ig) – 15Ig – 5 (I2 + Ig) = 0 10I1 – 30Ig –5I2 = 0 2I1 – 6Ig – I2 = 0 [3
1
3099-3102
Calculate the current through the galvanometer when a potential difference of 10 V is maintained across AC Solution Considering the mesh BADB, we have 100I1 + 15Ig – 60I2 = 0 or 20I1 + 3Ig – 12I2= 0 [3 65(a)] Considering the mesh BCDB, we have 10 (I1 – Ig) – 15Ig – 5 (I2 + Ig) = 0 10I1 – 30Ig –5I2 = 0 2I1 – 6Ig – I2 = 0 [3 65(b)] Considering the mesh ADCEA, 60I2 + 5 (I2 + Ig) = 10 65I2 + 5Ig = 10 13I2 + Ig = 2 [3
1
3100-3103
Solution Considering the mesh BADB, we have 100I1 + 15Ig – 60I2 = 0 or 20I1 + 3Ig – 12I2= 0 [3 65(a)] Considering the mesh BCDB, we have 10 (I1 – Ig) – 15Ig – 5 (I2 + Ig) = 0 10I1 – 30Ig –5I2 = 0 2I1 – 6Ig – I2 = 0 [3 65(b)] Considering the mesh ADCEA, 60I2 + 5 (I2 + Ig) = 10 65I2 + 5Ig = 10 13I2 + Ig = 2 [3 65(c)] Multiplying Eq
1
3101-3104
65(a)] Considering the mesh BCDB, we have 10 (I1 – Ig) – 15Ig – 5 (I2 + Ig) = 0 10I1 – 30Ig –5I2 = 0 2I1 – 6Ig – I2 = 0 [3 65(b)] Considering the mesh ADCEA, 60I2 + 5 (I2 + Ig) = 10 65I2 + 5Ig = 10 13I2 + Ig = 2 [3 65(c)] Multiplying Eq (3
1
3102-3105
65(b)] Considering the mesh ADCEA, 60I2 + 5 (I2 + Ig) = 10 65I2 + 5Ig = 10 13I2 + Ig = 2 [3 65(c)] Multiplying Eq (3 65b) by 10 20I1 – 60Ig – 10I2 = 0 [3
1
3103-3106
65(c)] Multiplying Eq (3 65b) by 10 20I1 – 60Ig – 10I2 = 0 [3 65(d)] From Eqs
1
3104-3107
(3 65b) by 10 20I1 – 60Ig – 10I2 = 0 [3 65(d)] From Eqs (3
1
3105-3108
65b) by 10 20I1 – 60Ig – 10I2 = 0 [3 65(d)] From Eqs (3 65d) and (3
1
3106-3109
65(d)] From Eqs (3 65d) and (3 65a) we have 63Ig – 2I2 = 0 I2 = 31
1
3107-3110
(3 65d) and (3 65a) we have 63Ig – 2I2 = 0 I2 = 31 5Ig [3
1
3108-3111
65d) and (3 65a) we have 63Ig – 2I2 = 0 I2 = 31 5Ig [3 65(e)] Substituting the value of I2 into Eq
1
3109-3112
65a) we have 63Ig – 2I2 = 0 I2 = 31 5Ig [3 65(e)] Substituting the value of I2 into Eq [3
1
3110-3113
5Ig [3 65(e)] Substituting the value of I2 into Eq [3 65(c)], we get 13 (31
1
3111-3114
65(e)] Substituting the value of I2 into Eq [3 65(c)], we get 13 (31 5Ig ) + Ig = 2 410
1
3112-3115
[3 65(c)], we get 13 (31 5Ig ) + Ig = 2 410 5 Ig = 2 Ig = 4
1
3113-3116
65(c)], we get 13 (31 5Ig ) + Ig = 2 410 5 Ig = 2 Ig = 4 87 mA
1
3114-3117
5Ig ) + Ig = 2 410 5 Ig = 2 Ig = 4 87 mA SUMMARY 1
1
3115-3118
5 Ig = 2 Ig = 4 87 mA SUMMARY 1 Current through a given area of a conductor is the net charge passing per unit time through the area
1
3116-3119
87 mA SUMMARY 1 Current through a given area of a conductor is the net charge passing per unit time through the area 2
1
3117-3120
SUMMARY 1 Current through a given area of a conductor is the net charge passing per unit time through the area 2 To maintain a steady current, we must have a closed circuit in which an external agency moves electric charge from lower to higher potential energy
1
3118-3121
Current through a given area of a conductor is the net charge passing per unit time through the area 2 To maintain a steady current, we must have a closed circuit in which an external agency moves electric charge from lower to higher potential energy The work done per unit charge by the source in taking the charge from lower to higher potential energy (i
1
3119-3122
2 To maintain a steady current, we must have a closed circuit in which an external agency moves electric charge from lower to higher potential energy The work done per unit charge by the source in taking the charge from lower to higher potential energy (i e
1
3120-3123
To maintain a steady current, we must have a closed circuit in which an external agency moves electric charge from lower to higher potential energy The work done per unit charge by the source in taking the charge from lower to higher potential energy (i e , from one terminal of the source to the other) is called the electromotive force, or emf, of the source
1
3121-3124
The work done per unit charge by the source in taking the charge from lower to higher potential energy (i e , from one terminal of the source to the other) is called the electromotive force, or emf, of the source Note that the emf is not a force; it is the voltage difference between the two terminals of a source in open circuit
1
3122-3125
e , from one terminal of the source to the other) is called the electromotive force, or emf, of the source Note that the emf is not a force; it is the voltage difference between the two terminals of a source in open circuit 3
1
3123-3126
, from one terminal of the source to the other) is called the electromotive force, or emf, of the source Note that the emf is not a force; it is the voltage difference between the two terminals of a source in open circuit 3 Ohm’s law: The electric current I flowing through a substance is proportional to the voltage V across its ends, i
1
3124-3127
Note that the emf is not a force; it is the voltage difference between the two terminals of a source in open circuit 3 Ohm’s law: The electric current I flowing through a substance is proportional to the voltage V across its ends, i e
1
3125-3128
3 Ohm’s law: The electric current I flowing through a substance is proportional to the voltage V across its ends, i e , V µ I or V = RI, where R is called the resistance of the substance
1
3126-3129
Ohm’s law: The electric current I flowing through a substance is proportional to the voltage V across its ends, i e , V µ I or V = RI, where R is called the resistance of the substance The unit of resistance is ohm: 1W = 1 V A–1
1
3127-3130
e , V µ I or V = RI, where R is called the resistance of the substance The unit of resistance is ohm: 1W = 1 V A–1 Rationalised 2023-24 Current Electricity 103 4
1
3128-3131
, V µ I or V = RI, where R is called the resistance of the substance The unit of resistance is ohm: 1W = 1 V A–1 Rationalised 2023-24 Current Electricity 103 4 The resistance R of a conductor depends on its length l and cross-sectional area A through the relation, l R ρA = where r, called resistivity is a property of the material and depends on temperature and pressure
1
3129-3132
The unit of resistance is ohm: 1W = 1 V A–1 Rationalised 2023-24 Current Electricity 103 4 The resistance R of a conductor depends on its length l and cross-sectional area A through the relation, l R ρA = where r, called resistivity is a property of the material and depends on temperature and pressure 5
1
3130-3133
Rationalised 2023-24 Current Electricity 103 4 The resistance R of a conductor depends on its length l and cross-sectional area A through the relation, l R ρA = where r, called resistivity is a property of the material and depends on temperature and pressure 5 Electrical resistivity of substances varies over a very wide range
1
3131-3134
The resistance R of a conductor depends on its length l and cross-sectional area A through the relation, l R ρA = where r, called resistivity is a property of the material and depends on temperature and pressure 5 Electrical resistivity of substances varies over a very wide range Metals have low resistivity, in the range of 10–8 W m to 10–6 W m
1
3132-3135
5 Electrical resistivity of substances varies over a very wide range Metals have low resistivity, in the range of 10–8 W m to 10–6 W m Insulators like glass and rubber have 1022 to 1024 times greater resistivity
1
3133-3136
Electrical resistivity of substances varies over a very wide range Metals have low resistivity, in the range of 10–8 W m to 10–6 W m Insulators like glass and rubber have 1022 to 1024 times greater resistivity Semiconductors like Si and Ge lie roughly in the middle range of resistivity on a logarithmic scale
1
3134-3137
Metals have low resistivity, in the range of 10–8 W m to 10–6 W m Insulators like glass and rubber have 1022 to 1024 times greater resistivity Semiconductors like Si and Ge lie roughly in the middle range of resistivity on a logarithmic scale 6
1
3135-3138
Insulators like glass and rubber have 1022 to 1024 times greater resistivity Semiconductors like Si and Ge lie roughly in the middle range of resistivity on a logarithmic scale 6 In most substances, the carriers of current are electrons; in some cases, for example, ionic crystals and electrolytic liquids, positive and negative ions carry the electric current
1
3136-3139
Semiconductors like Si and Ge lie roughly in the middle range of resistivity on a logarithmic scale 6 In most substances, the carriers of current are electrons; in some cases, for example, ionic crystals and electrolytic liquids, positive and negative ions carry the electric current 7
1
3137-3140
6 In most substances, the carriers of current are electrons; in some cases, for example, ionic crystals and electrolytic liquids, positive and negative ions carry the electric current 7 Current density j gives the amount of charge flowing per second per unit area normal to the flow, j = nq vd where n is the number density (number per unit volume) of charge carriers each of charge q, and vd is the drift velocity of the charge carriers
1
3138-3141
In most substances, the carriers of current are electrons; in some cases, for example, ionic crystals and electrolytic liquids, positive and negative ions carry the electric current 7 Current density j gives the amount of charge flowing per second per unit area normal to the flow, j = nq vd where n is the number density (number per unit volume) of charge carriers each of charge q, and vd is the drift velocity of the charge carriers For electrons q = – e
1
3139-3142
7 Current density j gives the amount of charge flowing per second per unit area normal to the flow, j = nq vd where n is the number density (number per unit volume) of charge carriers each of charge q, and vd is the drift velocity of the charge carriers For electrons q = – e If j is normal to a cross-sectional area A and is constant over the area, the magnitude of the current I through the area is nevd A
1
3140-3143
Current density j gives the amount of charge flowing per second per unit area normal to the flow, j = nq vd where n is the number density (number per unit volume) of charge carriers each of charge q, and vd is the drift velocity of the charge carriers For electrons q = – e If j is normal to a cross-sectional area A and is constant over the area, the magnitude of the current I through the area is nevd A 8
1
3141-3144
For electrons q = – e If j is normal to a cross-sectional area A and is constant over the area, the magnitude of the current I through the area is nevd A 8 Using E = V/l, I = nevd A, and Ohm’s law, one obtains 2 d eE ne v m ρm = The proportionality between the force eE on the electrons in a metal due to the external field E and the drift velocity vd (not acceleration) can be understood, if we assume that the electrons suffer collisions with ions in the metal, which deflect them randomly
1
3142-3145
If j is normal to a cross-sectional area A and is constant over the area, the magnitude of the current I through the area is nevd A 8 Using E = V/l, I = nevd A, and Ohm’s law, one obtains 2 d eE ne v m ρm = The proportionality between the force eE on the electrons in a metal due to the external field E and the drift velocity vd (not acceleration) can be understood, if we assume that the electrons suffer collisions with ions in the metal, which deflect them randomly If such collisions occur on an average at a time interval t, vd = at = eEt/m where a is the acceleration of the electron
1
3143-3146
8 Using E = V/l, I = nevd A, and Ohm’s law, one obtains 2 d eE ne v m ρm = The proportionality between the force eE on the electrons in a metal due to the external field E and the drift velocity vd (not acceleration) can be understood, if we assume that the electrons suffer collisions with ions in the metal, which deflect them randomly If such collisions occur on an average at a time interval t, vd = at = eEt/m where a is the acceleration of the electron This gives 2 m ne ρ τ = 9
1
3144-3147
Using E = V/l, I = nevd A, and Ohm’s law, one obtains 2 d eE ne v m ρm = The proportionality between the force eE on the electrons in a metal due to the external field E and the drift velocity vd (not acceleration) can be understood, if we assume that the electrons suffer collisions with ions in the metal, which deflect them randomly If such collisions occur on an average at a time interval t, vd = at = eEt/m where a is the acceleration of the electron This gives 2 m ne ρ τ = 9 In the temperature range in which resistivity increases linearly with temperature, the temperature coefficient of resistivity a is defined as the fractional increase in resistivity per unit increase in temperature
1
3145-3148
If such collisions occur on an average at a time interval t, vd = at = eEt/m where a is the acceleration of the electron This gives 2 m ne ρ τ = 9 In the temperature range in which resistivity increases linearly with temperature, the temperature coefficient of resistivity a is defined as the fractional increase in resistivity per unit increase in temperature 10
1
3146-3149
This gives 2 m ne ρ τ = 9 In the temperature range in which resistivity increases linearly with temperature, the temperature coefficient of resistivity a is defined as the fractional increase in resistivity per unit increase in temperature 10 Ohm’s law is obeyed by many substances, but it is not a fundamental law of nature
1
3147-3150
In the temperature range in which resistivity increases linearly with temperature, the temperature coefficient of resistivity a is defined as the fractional increase in resistivity per unit increase in temperature 10 Ohm’s law is obeyed by many substances, but it is not a fundamental law of nature It fails if (a) V depends on I non-linearly
1
3148-3151
10 Ohm’s law is obeyed by many substances, but it is not a fundamental law of nature It fails if (a) V depends on I non-linearly (b) the relation between V and I depends on the sign of V for the same absolute value of V
1
3149-3152
Ohm’s law is obeyed by many substances, but it is not a fundamental law of nature It fails if (a) V depends on I non-linearly (b) the relation between V and I depends on the sign of V for the same absolute value of V (c) The relation between V and I is non-unique
1
3150-3153
It fails if (a) V depends on I non-linearly (b) the relation between V and I depends on the sign of V for the same absolute value of V (c) The relation between V and I is non-unique An example of (a) is when r increases with I (even if temperature is kept fixed)
1
3151-3154
(b) the relation between V and I depends on the sign of V for the same absolute value of V (c) The relation between V and I is non-unique An example of (a) is when r increases with I (even if temperature is kept fixed) A rectifier combines features (a) and (b)
1
3152-3155
(c) The relation between V and I is non-unique An example of (a) is when r increases with I (even if temperature is kept fixed) A rectifier combines features (a) and (b) GaAs shows the feature (c)
1
3153-3156
An example of (a) is when r increases with I (even if temperature is kept fixed) A rectifier combines features (a) and (b) GaAs shows the feature (c) 11
1
3154-3157
A rectifier combines features (a) and (b) GaAs shows the feature (c) 11 When a source of emf e is connected to an external resistance R, the voltage Vext across R is given by Vext = IR = R R r ε + where r is the internal resistance of the source
1
3155-3158
GaAs shows the feature (c) 11 When a source of emf e is connected to an external resistance R, the voltage Vext across R is given by Vext = IR = R R r ε + where r is the internal resistance of the source Rationalised 2023-24 Physics 104 Physical Quantity Symbol Dimensions Unit Remark Electric current I [A] A SI base unit Charge Q, q [T A] C Voltage, Electric V [M L 2 T –3 A –1] V Work/charge potential difference Electromotive force e [M L 2 T –3 A –1] V Work/charge Resistance R [M L 2 T –3 A –2] W R = V/I Resistivity r [M L 3 T –3 A –2] W m R = rl/A Electrical s [M –1 L –3 T 3 A 2] S s = 1/r conductivity Electric field E [M L T –3 A –1] V m –1 Electric force charge Drift speed vd [L T –1] m s –1 vd e E m = τ Relaxation time t [T] s Current density j [L –2 A] A m –2 current/area Mobility m [M L 3 T –4 A –1] m 2 V –1s –1 vd/ E 12
1
3156-3159
11 When a source of emf e is connected to an external resistance R, the voltage Vext across R is given by Vext = IR = R R r ε + where r is the internal resistance of the source Rationalised 2023-24 Physics 104 Physical Quantity Symbol Dimensions Unit Remark Electric current I [A] A SI base unit Charge Q, q [T A] C Voltage, Electric V [M L 2 T –3 A –1] V Work/charge potential difference Electromotive force e [M L 2 T –3 A –1] V Work/charge Resistance R [M L 2 T –3 A –2] W R = V/I Resistivity r [M L 3 T –3 A –2] W m R = rl/A Electrical s [M –1 L –3 T 3 A 2] S s = 1/r conductivity Electric field E [M L T –3 A –1] V m –1 Electric force charge Drift speed vd [L T –1] m s –1 vd e E m = τ Relaxation time t [T] s Current density j [L –2 A] A m –2 current/area Mobility m [M L 3 T –4 A –1] m 2 V –1s –1 vd/ E 12 Kirchhoff’s Rules – (a) Junction Rule: At any junction of circuit elements, the sum of currents entering the junction must equal the sum of currents leaving it
1
3157-3160
When a source of emf e is connected to an external resistance R, the voltage Vext across R is given by Vext = IR = R R r ε + where r is the internal resistance of the source Rationalised 2023-24 Physics 104 Physical Quantity Symbol Dimensions Unit Remark Electric current I [A] A SI base unit Charge Q, q [T A] C Voltage, Electric V [M L 2 T –3 A –1] V Work/charge potential difference Electromotive force e [M L 2 T –3 A –1] V Work/charge Resistance R [M L 2 T –3 A –2] W R = V/I Resistivity r [M L 3 T –3 A –2] W m R = rl/A Electrical s [M –1 L –3 T 3 A 2] S s = 1/r conductivity Electric field E [M L T –3 A –1] V m –1 Electric force charge Drift speed vd [L T –1] m s –1 vd e E m = τ Relaxation time t [T] s Current density j [L –2 A] A m –2 current/area Mobility m [M L 3 T –4 A –1] m 2 V –1s –1 vd/ E 12 Kirchhoff’s Rules – (a) Junction Rule: At any junction of circuit elements, the sum of currents entering the junction must equal the sum of currents leaving it (b) Loop Rule: The algebraic sum of changes in potential around any closed loop must be zero
1
3158-3161
Rationalised 2023-24 Physics 104 Physical Quantity Symbol Dimensions Unit Remark Electric current I [A] A SI base unit Charge Q, q [T A] C Voltage, Electric V [M L 2 T –3 A –1] V Work/charge potential difference Electromotive force e [M L 2 T –3 A –1] V Work/charge Resistance R [M L 2 T –3 A –2] W R = V/I Resistivity r [M L 3 T –3 A –2] W m R = rl/A Electrical s [M –1 L –3 T 3 A 2] S s = 1/r conductivity Electric field E [M L T –3 A –1] V m –1 Electric force charge Drift speed vd [L T –1] m s –1 vd e E m = τ Relaxation time t [T] s Current density j [L –2 A] A m –2 current/area Mobility m [M L 3 T –4 A –1] m 2 V –1s –1 vd/ E 12 Kirchhoff’s Rules – (a) Junction Rule: At any junction of circuit elements, the sum of currents entering the junction must equal the sum of currents leaving it (b) Loop Rule: The algebraic sum of changes in potential around any closed loop must be zero 13
1
3159-3162
Kirchhoff’s Rules – (a) Junction Rule: At any junction of circuit elements, the sum of currents entering the junction must equal the sum of currents leaving it (b) Loop Rule: The algebraic sum of changes in potential around any closed loop must be zero 13 The Wheatstone bridge is an arrangement of four resistances – R1, R2, R3, R4 as shown in the text
1
3160-3163
(b) Loop Rule: The algebraic sum of changes in potential around any closed loop must be zero 13 The Wheatstone bridge is an arrangement of four resistances – R1, R2, R3, R4 as shown in the text The null-point condition is given by 3 1 2 4 R RR R = using which the value of one resistance can be determined, knowing the other three resistances
1
3161-3164
13 The Wheatstone bridge is an arrangement of four resistances – R1, R2, R3, R4 as shown in the text The null-point condition is given by 3 1 2 4 R RR R = using which the value of one resistance can be determined, knowing the other three resistances POINTS TO PONDER 1
1
3162-3165
The Wheatstone bridge is an arrangement of four resistances – R1, R2, R3, R4 as shown in the text The null-point condition is given by 3 1 2 4 R RR R = using which the value of one resistance can be determined, knowing the other three resistances POINTS TO PONDER 1 Current is a scalar although we represent current with an arrow
1
3163-3166
The null-point condition is given by 3 1 2 4 R RR R = using which the value of one resistance can be determined, knowing the other three resistances POINTS TO PONDER 1 Current is a scalar although we represent current with an arrow Currents do not obey the law of vector addition
1
3164-3167
POINTS TO PONDER 1 Current is a scalar although we represent current with an arrow Currents do not obey the law of vector addition That current is a scalar also follows from it’s definition
1
3165-3168
Current is a scalar although we represent current with an arrow Currents do not obey the law of vector addition That current is a scalar also follows from it’s definition The current I through an area of cross-section is given by the scalar product of two vectors: I = j
1
3166-3169
Currents do not obey the law of vector addition That current is a scalar also follows from it’s definition The current I through an area of cross-section is given by the scalar product of two vectors: I = j DS where j and DS are vectors
1
3167-3170
That current is a scalar also follows from it’s definition The current I through an area of cross-section is given by the scalar product of two vectors: I = j DS where j and DS are vectors Rationalised 2023-24 Current Electricity 105 2
1
3168-3171
The current I through an area of cross-section is given by the scalar product of two vectors: I = j DS where j and DS are vectors Rationalised 2023-24 Current Electricity 105 2 Refer to V-I curves of a resistor and a diode as drawn in the text
1
3169-3172
DS where j and DS are vectors Rationalised 2023-24 Current Electricity 105 2 Refer to V-I curves of a resistor and a diode as drawn in the text A resistor obeys Ohm’s law while a diode does not
1
3170-3173
Rationalised 2023-24 Current Electricity 105 2 Refer to V-I curves of a resistor and a diode as drawn in the text A resistor obeys Ohm’s law while a diode does not The assertion that V = IR is a statement of Ohm’s law is not true
1
3171-3174
Refer to V-I curves of a resistor and a diode as drawn in the text A resistor obeys Ohm’s law while a diode does not The assertion that V = IR is a statement of Ohm’s law is not true This equation defines resistance and it may be applied to all conducting devices whether they obey Ohm’s law or not
1
3172-3175
A resistor obeys Ohm’s law while a diode does not The assertion that V = IR is a statement of Ohm’s law is not true This equation defines resistance and it may be applied to all conducting devices whether they obey Ohm’s law or not The Ohm’s law asserts that the plot of I versus V is linear i
1
3173-3176
The assertion that V = IR is a statement of Ohm’s law is not true This equation defines resistance and it may be applied to all conducting devices whether they obey Ohm’s law or not The Ohm’s law asserts that the plot of I versus V is linear i e
1
3174-3177
This equation defines resistance and it may be applied to all conducting devices whether they obey Ohm’s law or not The Ohm’s law asserts that the plot of I versus V is linear i e , R is independent of V
1
3175-3178
The Ohm’s law asserts that the plot of I versus V is linear i e , R is independent of V Equation E = r j leads to another statement of Ohm’s law, i
1
3176-3179
e , R is independent of V Equation E = r j leads to another statement of Ohm’s law, i e
1
3177-3180
, R is independent of V Equation E = r j leads to another statement of Ohm’s law, i e , a conducting material obeys Ohm’s law when the resistivity of the material does not depend on the magnitude and direction of applied electric field
1
3178-3181
Equation E = r j leads to another statement of Ohm’s law, i e , a conducting material obeys Ohm’s law when the resistivity of the material does not depend on the magnitude and direction of applied electric field 3
1
3179-3182
e , a conducting material obeys Ohm’s law when the resistivity of the material does not depend on the magnitude and direction of applied electric field 3 Homogeneous conductors like silver or semiconductors like pure germanium or germanium containing impurities obey Ohm’s law within some range of electric field values
1
3180-3183
, a conducting material obeys Ohm’s law when the resistivity of the material does not depend on the magnitude and direction of applied electric field 3 Homogeneous conductors like silver or semiconductors like pure germanium or germanium containing impurities obey Ohm’s law within some range of electric field values If the field becomes too strong, there are departures from Ohm’s law in all cases
1
3181-3184
3 Homogeneous conductors like silver or semiconductors like pure germanium or germanium containing impurities obey Ohm’s law within some range of electric field values If the field becomes too strong, there are departures from Ohm’s law in all cases 4
1
3182-3185
Homogeneous conductors like silver or semiconductors like pure germanium or germanium containing impurities obey Ohm’s law within some range of electric field values If the field becomes too strong, there are departures from Ohm’s law in all cases 4 Motion of conduction electrons in electric field E is the sum of (i) motion due to random collisions and (ii) that due to E
1
3183-3186
If the field becomes too strong, there are departures from Ohm’s law in all cases 4 Motion of conduction electrons in electric field E is the sum of (i) motion due to random collisions and (ii) that due to E The motion due to random collisions averages to zero and does not contribute to vd (Chapter 11, Textbook of Class XI)
1
3184-3187
4 Motion of conduction electrons in electric field E is the sum of (i) motion due to random collisions and (ii) that due to E The motion due to random collisions averages to zero and does not contribute to vd (Chapter 11, Textbook of Class XI) vd , thus is only due to applied electric field on the electron
1
3185-3188
Motion of conduction electrons in electric field E is the sum of (i) motion due to random collisions and (ii) that due to E The motion due to random collisions averages to zero and does not contribute to vd (Chapter 11, Textbook of Class XI) vd , thus is only due to applied electric field on the electron 5
1
3186-3189
The motion due to random collisions averages to zero and does not contribute to vd (Chapter 11, Textbook of Class XI) vd , thus is only due to applied electric field on the electron 5 The relation j = r v should be applied to each type of charge carriers separately
1
3187-3190
vd , thus is only due to applied electric field on the electron 5 The relation j = r v should be applied to each type of charge carriers separately In a conducting wire, the total current and charge density arises from both positive and negative charges: j = r+ v+ + r– v– rrrrr = r+ + r– Now in a neutral wire carrying electric current, rrrrr+ = – r– Further, v+ ~ 0 which gives rrrrr = 0 j = r– v Thus, the relation j = r v does not apply to the total current charge density
1
3188-3191
5 The relation j = r v should be applied to each type of charge carriers separately In a conducting wire, the total current and charge density arises from both positive and negative charges: j = r+ v+ + r– v– rrrrr = r+ + r– Now in a neutral wire carrying electric current, rrrrr+ = – r– Further, v+ ~ 0 which gives rrrrr = 0 j = r– v Thus, the relation j = r v does not apply to the total current charge density 6
1
3189-3192
The relation j = r v should be applied to each type of charge carriers separately In a conducting wire, the total current and charge density arises from both positive and negative charges: j = r+ v+ + r– v– rrrrr = r+ + r– Now in a neutral wire carrying electric current, rrrrr+ = – r– Further, v+ ~ 0 which gives rrrrr = 0 j = r– v Thus, the relation j = r v does not apply to the total current charge density 6 Kirchhoff’s junction rule is based on conservation of charge and the outgoing currents add up and are equal to incoming current at a junction