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1
2790-2793
3) =(75 3) 1 70 10 × × = 820 °C that is, T2 = (820 + 27 0) °C = 847 °C Thus, the steady temperature of the heating element (when heating effect due to the current equals heat loss to the surroundings) is 847 °C
1
2791-2794
3) 1 70 10 × × = 820 °C that is, T2 = (820 + 27 0) °C = 847 °C Thus, the steady temperature of the heating element (when heating effect due to the current equals heat loss to the surroundings) is 847 °C Rationalised 2023-24 Physics 92 EXAMPLE 3
1
2792-2795
70 10 × × = 820 °C that is, T2 = (820 + 27 0) °C = 847 °C Thus, the steady temperature of the heating element (when heating effect due to the current equals heat loss to the surroundings) is 847 °C Rationalised 2023-24 Physics 92 EXAMPLE 3 4 Example 3
1
2793-2796
0) °C = 847 °C Thus, the steady temperature of the heating element (when heating effect due to the current equals heat loss to the surroundings) is 847 °C Rationalised 2023-24 Physics 92 EXAMPLE 3 4 Example 3 4 The resistance of the platinum wire of a platinum resistance thermometer at the ice point is 5 W and at steam point is 5
1
2794-2797
Rationalised 2023-24 Physics 92 EXAMPLE 3 4 Example 3 4 The resistance of the platinum wire of a platinum resistance thermometer at the ice point is 5 W and at steam point is 5 23 W
1
2795-2798
4 Example 3 4 The resistance of the platinum wire of a platinum resistance thermometer at the ice point is 5 W and at steam point is 5 23 W When the thermometer is inserted in a hot bath, the resistance of the platinum wire is 5
1
2796-2799
4 The resistance of the platinum wire of a platinum resistance thermometer at the ice point is 5 W and at steam point is 5 23 W When the thermometer is inserted in a hot bath, the resistance of the platinum wire is 5 795 W
1
2797-2800
23 W When the thermometer is inserted in a hot bath, the resistance of the platinum wire is 5 795 W Calculate the temperature of the bath
1
2798-2801
When the thermometer is inserted in a hot bath, the resistance of the platinum wire is 5 795 W Calculate the temperature of the bath Solution R0 = 5 W, R100 = 5
1
2799-2802
795 W Calculate the temperature of the bath Solution R0 = 5 W, R100 = 5 23 W and Rt = 5
1
2800-2803
Calculate the temperature of the bath Solution R0 = 5 W, R100 = 5 23 W and Rt = 5 795 W Now, 0 0 100 0 100, (1 ) t t R R t R R t R R α − = × = + − 5
1
2801-2804
Solution R0 = 5 W, R100 = 5 23 W and Rt = 5 795 W Now, 0 0 100 0 100, (1 ) t t R R t R R t R R α − = × = + − 5 795 5 100 5
1
2802-2805
23 W and Rt = 5 795 W Now, 0 0 100 0 100, (1 ) t t R R t R R t R R α − = × = + − 5 795 5 100 5 23 −5 = × − = 0
1
2803-2806
795 W Now, 0 0 100 0 100, (1 ) t t R R t R R t R R α − = × = + − 5 795 5 100 5 23 −5 = × − = 0 795 0
1
2804-2807
795 5 100 5 23 −5 = × − = 0 795 0 23 ×100 = 345
1
2805-2808
23 −5 = × − = 0 795 0 23 ×100 = 345 65 °C 3
1
2806-2809
795 0 23 ×100 = 345 65 °C 3 9 ELECTRICAL ENERGY, POWER Consider a conductor with end points A and B, in which a current I is flowing from A to B
1
2807-2810
23 ×100 = 345 65 °C 3 9 ELECTRICAL ENERGY, POWER Consider a conductor with end points A and B, in which a current I is flowing from A to B The electric potential at A and B are denoted by V(A) and V(B) respectively
1
2808-2811
65 °C 3 9 ELECTRICAL ENERGY, POWER Consider a conductor with end points A and B, in which a current I is flowing from A to B The electric potential at A and B are denoted by V(A) and V(B) respectively Since current is flowing from A to B, V(A) > V(B) and the potential difference across AB is V = V(A) – V(B) > 0
1
2809-2812
9 ELECTRICAL ENERGY, POWER Consider a conductor with end points A and B, in which a current I is flowing from A to B The electric potential at A and B are denoted by V(A) and V(B) respectively Since current is flowing from A to B, V(A) > V(B) and the potential difference across AB is V = V(A) – V(B) > 0 In a time interval Dt, an amount of charge DQ = I Dt travels from A to B
1
2810-2813
The electric potential at A and B are denoted by V(A) and V(B) respectively Since current is flowing from A to B, V(A) > V(B) and the potential difference across AB is V = V(A) – V(B) > 0 In a time interval Dt, an amount of charge DQ = I Dt travels from A to B The potential energy of the charge at A, by definition, was Q V(A) and similarly at B, it is Q V(B)
1
2811-2814
Since current is flowing from A to B, V(A) > V(B) and the potential difference across AB is V = V(A) – V(B) > 0 In a time interval Dt, an amount of charge DQ = I Dt travels from A to B The potential energy of the charge at A, by definition, was Q V(A) and similarly at B, it is Q V(B) Thus, change in its potential energy DUpot is DUpot = Final potential energy – Initial potential energy = DQ[(V (B) – V (A)] = –DQ V = –I VDt < 0 (3
1
2812-2815
In a time interval Dt, an amount of charge DQ = I Dt travels from A to B The potential energy of the charge at A, by definition, was Q V(A) and similarly at B, it is Q V(B) Thus, change in its potential energy DUpot is DUpot = Final potential energy – Initial potential energy = DQ[(V (B) – V (A)] = –DQ V = –I VDt < 0 (3 28) If charges moved without collisions through the conductor, their kinetic energy would also change so that the total energy is unchanged
1
2813-2816
The potential energy of the charge at A, by definition, was Q V(A) and similarly at B, it is Q V(B) Thus, change in its potential energy DUpot is DUpot = Final potential energy – Initial potential energy = DQ[(V (B) – V (A)] = –DQ V = –I VDt < 0 (3 28) If charges moved without collisions through the conductor, their kinetic energy would also change so that the total energy is unchanged Conservation of total energy would then imply that, DK = –DUpot (3
1
2814-2817
Thus, change in its potential energy DUpot is DUpot = Final potential energy – Initial potential energy = DQ[(V (B) – V (A)] = –DQ V = –I VDt < 0 (3 28) If charges moved without collisions through the conductor, their kinetic energy would also change so that the total energy is unchanged Conservation of total energy would then imply that, DK = –DUpot (3 29) that is, DK = I VDt > 0 (3
1
2815-2818
28) If charges moved without collisions through the conductor, their kinetic energy would also change so that the total energy is unchanged Conservation of total energy would then imply that, DK = –DUpot (3 29) that is, DK = I VDt > 0 (3 30) Thus, in case charges were moving freely through the conductor under the action of electric field, their kinetic energy would increase as they move
1
2816-2819
Conservation of total energy would then imply that, DK = –DUpot (3 29) that is, DK = I VDt > 0 (3 30) Thus, in case charges were moving freely through the conductor under the action of electric field, their kinetic energy would increase as they move We have, however, seen earlier that on the average, charge carriers do not move with acceleration but with a steady drift velocity
1
2817-2820
29) that is, DK = I VDt > 0 (3 30) Thus, in case charges were moving freely through the conductor under the action of electric field, their kinetic energy would increase as they move We have, however, seen earlier that on the average, charge carriers do not move with acceleration but with a steady drift velocity This is because of the collisions with ions and atoms during transit
1
2818-2821
30) Thus, in case charges were moving freely through the conductor under the action of electric field, their kinetic energy would increase as they move We have, however, seen earlier that on the average, charge carriers do not move with acceleration but with a steady drift velocity This is because of the collisions with ions and atoms during transit During collisions, the energy gained by the charges thus is shared with the atoms
1
2819-2822
We have, however, seen earlier that on the average, charge carriers do not move with acceleration but with a steady drift velocity This is because of the collisions with ions and atoms during transit During collisions, the energy gained by the charges thus is shared with the atoms The atoms vibrate more vigorously, i
1
2820-2823
This is because of the collisions with ions and atoms during transit During collisions, the energy gained by the charges thus is shared with the atoms The atoms vibrate more vigorously, i e
1
2821-2824
During collisions, the energy gained by the charges thus is shared with the atoms The atoms vibrate more vigorously, i e , the conductor heats up
1
2822-2825
The atoms vibrate more vigorously, i e , the conductor heats up Thus, in an actual conductor, an amount of energy dissipated as heat in the conductor during the time interval Dt is, DW = I VDt (3
1
2823-2826
e , the conductor heats up Thus, in an actual conductor, an amount of energy dissipated as heat in the conductor during the time interval Dt is, DW = I VDt (3 31) The energy dissipated per unit time is the power dissipated P = DW/Dt and we have, P = I V (3
1
2824-2827
, the conductor heats up Thus, in an actual conductor, an amount of energy dissipated as heat in the conductor during the time interval Dt is, DW = I VDt (3 31) The energy dissipated per unit time is the power dissipated P = DW/Dt and we have, P = I V (3 32) Rationalised 2023-24 Current Electricity 93 Using Ohm’s law V = IR, we get P = I 2 R = V 2/R (3
1
2825-2828
Thus, in an actual conductor, an amount of energy dissipated as heat in the conductor during the time interval Dt is, DW = I VDt (3 31) The energy dissipated per unit time is the power dissipated P = DW/Dt and we have, P = I V (3 32) Rationalised 2023-24 Current Electricity 93 Using Ohm’s law V = IR, we get P = I 2 R = V 2/R (3 33) as the power loss (“ohmic loss”) in a conductor of resistance R carrying a current I
1
2826-2829
31) The energy dissipated per unit time is the power dissipated P = DW/Dt and we have, P = I V (3 32) Rationalised 2023-24 Current Electricity 93 Using Ohm’s law V = IR, we get P = I 2 R = V 2/R (3 33) as the power loss (“ohmic loss”) in a conductor of resistance R carrying a current I It is this power which heats up, for example, the coil of an electric bulb to incandescence, radiating out heat and light
1
2827-2830
32) Rationalised 2023-24 Current Electricity 93 Using Ohm’s law V = IR, we get P = I 2 R = V 2/R (3 33) as the power loss (“ohmic loss”) in a conductor of resistance R carrying a current I It is this power which heats up, for example, the coil of an electric bulb to incandescence, radiating out heat and light Where does the power come from
1
2828-2831
33) as the power loss (“ohmic loss”) in a conductor of resistance R carrying a current I It is this power which heats up, for example, the coil of an electric bulb to incandescence, radiating out heat and light Where does the power come from As we have reasoned before, we need an external source to keep a steady current through the conductor
1
2829-2832
It is this power which heats up, for example, the coil of an electric bulb to incandescence, radiating out heat and light Where does the power come from As we have reasoned before, we need an external source to keep a steady current through the conductor It is clearly this source which must supply this power
1
2830-2833
Where does the power come from As we have reasoned before, we need an external source to keep a steady current through the conductor It is clearly this source which must supply this power In the simple circuit shown with a cell (Fig
1
2831-2834
As we have reasoned before, we need an external source to keep a steady current through the conductor It is clearly this source which must supply this power In the simple circuit shown with a cell (Fig 3
1
2832-2835
It is clearly this source which must supply this power In the simple circuit shown with a cell (Fig 3 11), it is the chemical energy of the cell which supplies this power for as long as it can
1
2833-2836
In the simple circuit shown with a cell (Fig 3 11), it is the chemical energy of the cell which supplies this power for as long as it can The expressions for power, Eqs
1
2834-2837
3 11), it is the chemical energy of the cell which supplies this power for as long as it can The expressions for power, Eqs (3
1
2835-2838
11), it is the chemical energy of the cell which supplies this power for as long as it can The expressions for power, Eqs (3 32) and (3
1
2836-2839
The expressions for power, Eqs (3 32) and (3 33), show the dependence of the power dissipated in a resistor R on the current through it and the voltage across it
1
2837-2840
(3 32) and (3 33), show the dependence of the power dissipated in a resistor R on the current through it and the voltage across it Equation (3
1
2838-2841
32) and (3 33), show the dependence of the power dissipated in a resistor R on the current through it and the voltage across it Equation (3 33) has an important application to power transmission
1
2839-2842
33), show the dependence of the power dissipated in a resistor R on the current through it and the voltage across it Equation (3 33) has an important application to power transmission Electrical power is transmitted from power stations to homes and factories, which may be hundreds of miles away, via transmission cables
1
2840-2843
Equation (3 33) has an important application to power transmission Electrical power is transmitted from power stations to homes and factories, which may be hundreds of miles away, via transmission cables One obviously wants to minimise the power loss in the transmission cables connecting the power stations to homes and factories
1
2841-2844
33) has an important application to power transmission Electrical power is transmitted from power stations to homes and factories, which may be hundreds of miles away, via transmission cables One obviously wants to minimise the power loss in the transmission cables connecting the power stations to homes and factories We shall see now how this can be achieved
1
2842-2845
Electrical power is transmitted from power stations to homes and factories, which may be hundreds of miles away, via transmission cables One obviously wants to minimise the power loss in the transmission cables connecting the power stations to homes and factories We shall see now how this can be achieved Consider a device R, to which a power P is to be delivered via transmission cables having a resistance Rc to be dissipated by it finally
1
2843-2846
One obviously wants to minimise the power loss in the transmission cables connecting the power stations to homes and factories We shall see now how this can be achieved Consider a device R, to which a power P is to be delivered via transmission cables having a resistance Rc to be dissipated by it finally If V is the voltage across R and I the current through it, then P = V I (3
1
2844-2847
We shall see now how this can be achieved Consider a device R, to which a power P is to be delivered via transmission cables having a resistance Rc to be dissipated by it finally If V is the voltage across R and I the current through it, then P = V I (3 34) The connecting wires from the power station to the device has a finite resistance Rc
1
2845-2848
Consider a device R, to which a power P is to be delivered via transmission cables having a resistance Rc to be dissipated by it finally If V is the voltage across R and I the current through it, then P = V I (3 34) The connecting wires from the power station to the device has a finite resistance Rc The power dissipated in the connecting wires, which is wasted is Pc with Pc = I 2 Rc 2 2 c P R V = (3
1
2846-2849
If V is the voltage across R and I the current through it, then P = V I (3 34) The connecting wires from the power station to the device has a finite resistance Rc The power dissipated in the connecting wires, which is wasted is Pc with Pc = I 2 Rc 2 2 c P R V = (3 35) from Eq
1
2847-2850
34) The connecting wires from the power station to the device has a finite resistance Rc The power dissipated in the connecting wires, which is wasted is Pc with Pc = I 2 Rc 2 2 c P R V = (3 35) from Eq (3
1
2848-2851
The power dissipated in the connecting wires, which is wasted is Pc with Pc = I 2 Rc 2 2 c P R V = (3 35) from Eq (3 32)
1
2849-2852
35) from Eq (3 32) Thus, to drive a device of power P, the power wasted in the connecting wires is inversely proportional to V 2
1
2850-2853
(3 32) Thus, to drive a device of power P, the power wasted in the connecting wires is inversely proportional to V 2 The transmission cables from power stations are hundreds of miles long and their resistance Rc is considerable
1
2851-2854
32) Thus, to drive a device of power P, the power wasted in the connecting wires is inversely proportional to V 2 The transmission cables from power stations are hundreds of miles long and their resistance Rc is considerable To reduce Pc, these wires carry current at enormous values of V and this is the reason for the high voltage danger signs on transmission lines — a common sight as we move away from populated areas
1
2852-2855
Thus, to drive a device of power P, the power wasted in the connecting wires is inversely proportional to V 2 The transmission cables from power stations are hundreds of miles long and their resistance Rc is considerable To reduce Pc, these wires carry current at enormous values of V and this is the reason for the high voltage danger signs on transmission lines — a common sight as we move away from populated areas Using electricity at such voltages is not safe and hence at the other end, a device called a transformer lowers the voltage to a value suitable for use
1
2853-2856
The transmission cables from power stations are hundreds of miles long and their resistance Rc is considerable To reduce Pc, these wires carry current at enormous values of V and this is the reason for the high voltage danger signs on transmission lines — a common sight as we move away from populated areas Using electricity at such voltages is not safe and hence at the other end, a device called a transformer lowers the voltage to a value suitable for use 3
1
2854-2857
To reduce Pc, these wires carry current at enormous values of V and this is the reason for the high voltage danger signs on transmission lines — a common sight as we move away from populated areas Using electricity at such voltages is not safe and hence at the other end, a device called a transformer lowers the voltage to a value suitable for use 3 10 CELLS, EMF, INTERNAL RESISTANCE We have already mentioned that a simple device to maintain a steady current in an electric circuit is the electrolytic cell
1
2855-2858
Using electricity at such voltages is not safe and hence at the other end, a device called a transformer lowers the voltage to a value suitable for use 3 10 CELLS, EMF, INTERNAL RESISTANCE We have already mentioned that a simple device to maintain a steady current in an electric circuit is the electrolytic cell Basically a cell has two electrodes, called the positive (P) and the negative (N), as shown in FIGURE 3
1
2856-2859
3 10 CELLS, EMF, INTERNAL RESISTANCE We have already mentioned that a simple device to maintain a steady current in an electric circuit is the electrolytic cell Basically a cell has two electrodes, called the positive (P) and the negative (N), as shown in FIGURE 3 11 Heat is produced in the resistor R which is connected across the terminals of a cell
1
2857-2860
10 CELLS, EMF, INTERNAL RESISTANCE We have already mentioned that a simple device to maintain a steady current in an electric circuit is the electrolytic cell Basically a cell has two electrodes, called the positive (P) and the negative (N), as shown in FIGURE 3 11 Heat is produced in the resistor R which is connected across the terminals of a cell The energy dissipated in the resistor R comes from the chemical energy of the electrolyte
1
2858-2861
Basically a cell has two electrodes, called the positive (P) and the negative (N), as shown in FIGURE 3 11 Heat is produced in the resistor R which is connected across the terminals of a cell The energy dissipated in the resistor R comes from the chemical energy of the electrolyte Rationalised 2023-24 Physics 94 Fig
1
2859-2862
11 Heat is produced in the resistor R which is connected across the terminals of a cell The energy dissipated in the resistor R comes from the chemical energy of the electrolyte Rationalised 2023-24 Physics 94 Fig 3
1
2860-2863
The energy dissipated in the resistor R comes from the chemical energy of the electrolyte Rationalised 2023-24 Physics 94 Fig 3 12
1
2861-2864
Rationalised 2023-24 Physics 94 Fig 3 12 They are immersed in an electrolytic solution
1
2862-2865
3 12 They are immersed in an electrolytic solution Dipped in the solution, the electrodes exchange charges with the electrolyte
1
2863-2866
12 They are immersed in an electrolytic solution Dipped in the solution, the electrodes exchange charges with the electrolyte The positive electrode has a potential difference V+ (V+ > 0) between itself and the electrolyte solution immediately adjacent to it marked A in the figure
1
2864-2867
They are immersed in an electrolytic solution Dipped in the solution, the electrodes exchange charges with the electrolyte The positive electrode has a potential difference V+ (V+ > 0) between itself and the electrolyte solution immediately adjacent to it marked A in the figure Similarly, the negative electrode develops a negative potential – (V– ) (V– ≥ 0) relative to the electrolyte adjacent to it, marked as B in the figure
1
2865-2868
Dipped in the solution, the electrodes exchange charges with the electrolyte The positive electrode has a potential difference V+ (V+ > 0) between itself and the electrolyte solution immediately adjacent to it marked A in the figure Similarly, the negative electrode develops a negative potential – (V– ) (V– ≥ 0) relative to the electrolyte adjacent to it, marked as B in the figure When there is no current, the electrolyte has the same potential throughout, so that the potential difference between P and N is V+ – (–V–) = V+ + V–
1
2866-2869
The positive electrode has a potential difference V+ (V+ > 0) between itself and the electrolyte solution immediately adjacent to it marked A in the figure Similarly, the negative electrode develops a negative potential – (V– ) (V– ≥ 0) relative to the electrolyte adjacent to it, marked as B in the figure When there is no current, the electrolyte has the same potential throughout, so that the potential difference between P and N is V+ – (–V–) = V+ + V– This difference is called the electromotive force (emf) of the cell and is denoted by e
1
2867-2870
Similarly, the negative electrode develops a negative potential – (V– ) (V– ≥ 0) relative to the electrolyte adjacent to it, marked as B in the figure When there is no current, the electrolyte has the same potential throughout, so that the potential difference between P and N is V+ – (–V–) = V+ + V– This difference is called the electromotive force (emf) of the cell and is denoted by e Thus e = V++V– > 0 (3
1
2868-2871
When there is no current, the electrolyte has the same potential throughout, so that the potential difference between P and N is V+ – (–V–) = V+ + V– This difference is called the electromotive force (emf) of the cell and is denoted by e Thus e = V++V– > 0 (3 36) Note that e is, actually, a potential difference and not a force
1
2869-2872
This difference is called the electromotive force (emf) of the cell and is denoted by e Thus e = V++V– > 0 (3 36) Note that e is, actually, a potential difference and not a force The name emf, however, is used because of historical reasons, and was given at a time when the phenomenon was not understood properly
1
2870-2873
Thus e = V++V– > 0 (3 36) Note that e is, actually, a potential difference and not a force The name emf, however, is used because of historical reasons, and was given at a time when the phenomenon was not understood properly To understand the significance of e, consider a resistor R connected across the cell (Fig
1
2871-2874
36) Note that e is, actually, a potential difference and not a force The name emf, however, is used because of historical reasons, and was given at a time when the phenomenon was not understood properly To understand the significance of e, consider a resistor R connected across the cell (Fig 3
1
2872-2875
The name emf, however, is used because of historical reasons, and was given at a time when the phenomenon was not understood properly To understand the significance of e, consider a resistor R connected across the cell (Fig 3 12)
1
2873-2876
To understand the significance of e, consider a resistor R connected across the cell (Fig 3 12) A current I flows across R from C to D
1
2874-2877
3 12) A current I flows across R from C to D As explained before, a steady current is maintained because current flows from N to P through the electrolyte
1
2875-2878
12) A current I flows across R from C to D As explained before, a steady current is maintained because current flows from N to P through the electrolyte Clearly, across the electrolyte the same current flows through the electrolyte but from N to P, whereas through R, it flows from P to N
1
2876-2879
A current I flows across R from C to D As explained before, a steady current is maintained because current flows from N to P through the electrolyte Clearly, across the electrolyte the same current flows through the electrolyte but from N to P, whereas through R, it flows from P to N The electrolyte through which a current flows has a finite resistance r, called the internal resistance
1
2877-2880
As explained before, a steady current is maintained because current flows from N to P through the electrolyte Clearly, across the electrolyte the same current flows through the electrolyte but from N to P, whereas through R, it flows from P to N The electrolyte through which a current flows has a finite resistance r, called the internal resistance Consider first the situation when R is infinite so that I = V/R = 0, where V is the potential difference between P and N
1
2878-2881
Clearly, across the electrolyte the same current flows through the electrolyte but from N to P, whereas through R, it flows from P to N The electrolyte through which a current flows has a finite resistance r, called the internal resistance Consider first the situation when R is infinite so that I = V/R = 0, where V is the potential difference between P and N Now, V = Potential difference between P and A + Potential difference between A and B + Potential difference between B and N = e (3
1
2879-2882
The electrolyte through which a current flows has a finite resistance r, called the internal resistance Consider first the situation when R is infinite so that I = V/R = 0, where V is the potential difference between P and N Now, V = Potential difference between P and A + Potential difference between A and B + Potential difference between B and N = e (3 37) Thus, emf e is the potential difference between the positive and negative electrodes in an open circuit, i
1
2880-2883
Consider first the situation when R is infinite so that I = V/R = 0, where V is the potential difference between P and N Now, V = Potential difference between P and A + Potential difference between A and B + Potential difference between B and N = e (3 37) Thus, emf e is the potential difference between the positive and negative electrodes in an open circuit, i e
1
2881-2884
Now, V = Potential difference between P and A + Potential difference between A and B + Potential difference between B and N = e (3 37) Thus, emf e is the potential difference between the positive and negative electrodes in an open circuit, i e , when no current is flowing through the cell
1
2882-2885
37) Thus, emf e is the potential difference between the positive and negative electrodes in an open circuit, i e , when no current is flowing through the cell If however R is finite, I is not zero
1
2883-2886
e , when no current is flowing through the cell If however R is finite, I is not zero In that case the potential difference between P and N is V = V++ V– – I r = e – I r (3
1
2884-2887
, when no current is flowing through the cell If however R is finite, I is not zero In that case the potential difference between P and N is V = V++ V– – I r = e – I r (3 38) Note the negative sign in the expression (I r) for the potential difference between A and B
1
2885-2888
If however R is finite, I is not zero In that case the potential difference between P and N is V = V++ V– – I r = e – I r (3 38) Note the negative sign in the expression (I r) for the potential difference between A and B This is because the current I flows from B to A in the electrolyte
1
2886-2889
In that case the potential difference between P and N is V = V++ V– – I r = e – I r (3 38) Note the negative sign in the expression (I r) for the potential difference between A and B This is because the current I flows from B to A in the electrolyte In practical calculations, internal resistances of cells in the circuit may be neglected when the current I is such that e >> I r
1
2887-2890
38) Note the negative sign in the expression (I r) for the potential difference between A and B This is because the current I flows from B to A in the electrolyte In practical calculations, internal resistances of cells in the circuit may be neglected when the current I is such that e >> I r The actual values of the internal resistances of cells vary from cell to cell
1
2888-2891
This is because the current I flows from B to A in the electrolyte In practical calculations, internal resistances of cells in the circuit may be neglected when the current I is such that e >> I r The actual values of the internal resistances of cells vary from cell to cell The internal resistance of dry cells, however, is much higher than the common electrolytic cells
1
2889-2892
In practical calculations, internal resistances of cells in the circuit may be neglected when the current I is such that e >> I r The actual values of the internal resistances of cells vary from cell to cell The internal resistance of dry cells, however, is much higher than the common electrolytic cells We also observe that since V is the potential difference across R, we have from Ohm’s law V = I R (3