Question 3.2: A battery of emf 10 V and internal resistance 3 Ω is connected to a resistor. If the current in the circuit is 0.5 A, what is the resistance of the resistor? What is the terminal voltage of the battery when the circuit is closed?
Class 12 - Physics - Current Electricity Current Electricity Page-127
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emf of battery, E = 10V
internal resistance of battery , r = 3 ohm
current in the circuit is I = 0.5 A.
so, use Kirchoff's law,
E - Ir - IR = 0 [ see figure ]
I = E/(R + r) = 10/(R + 3)
0.5(R + 3) = 10
R + 3 = 20 => R = 17 ohm
now, let terminal voltage of the battery when the circuit is closed is V
V = E - Ir
= 10 - 0.5 × 3 = 10 - 1.5 = 8.5 V
hence, terminal voltage is 8.5 V
internal resistance of battery , r = 3 ohm
current in the circuit is I = 0.5 A.
so, use Kirchoff's law,
E - Ir - IR = 0 [ see figure ]
I = E/(R + r) = 10/(R + 3)
0.5(R + 3) = 10
R + 3 = 20 => R = 17 ohm
now, let terminal voltage of the battery when the circuit is closed is V
V = E - Ir
= 10 - 0.5 × 3 = 10 - 1.5 = 8.5 V
hence, terminal voltage is 8.5 V
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