(i) The potential difference across the two ends of a circuit component is decreased to one-third of its…
(i) The potential difference across the two ends of a circuit component is decreased to one-third of its initial value, while its resistance remains constant. What change will be observed in the current flowing through it ? Name and state the law which helps us to answer this question.
(ii) Draw a schematic diagram of a circuit consisting of a battery of four 1.5 V cells, a 5 Ω resistor, a 10 Ω resistor and a 15 Ω resistor and a plug key, all connected in series. Now find (I) the electric current passing through the circuit, and (II) potential difference across the 10 Ω resistor when the plug key is closed.
Solution
(a)
(i) Current becomes one-third of its initial value.
Ohm's Law
The potential difference across the ends of a conductor is directly proportional to the current flowing through it, provided its temperature remains the same.
(ii) [circuit diagram: R1=5Ω, R2=10Ω, R3=15Ω in series with a 6V battery and key K]
Total Voltage = V = 4 × 1.5 V = 6 V
Total resistance, R(s) = R1 + R2 + R3 = 5Ω + 10Ω + 15Ω = 30Ω
(I) Current, I = V/R = 6V/30Ω = 0.2 A
(II) V = IR = 0.2 A × 10 Ω = 2 V