JEE Main 2024 · 30 January · morning · Single correct · +4 / −1
Primary coil of a transformer is connected to 220 V ac. Primary and secondary turns of the transforms are 100 and 10 respectively. Secondary coil of transformer is connected to two series resistances shown in figure. The output voltage (V₀) is :
- (a) 7 V
- (b) 44 V
- (c) 22 V
- (d) 15 V
Answer and solution
Answer (a) 7 V
Solution
Physics sir · 3 steps
First step the voltage down by the turns ratio, then share it between the two resistors in series.
- Secondary voltage. For an ideal transformer, Vₛ/Vₚ = Nₛ/Nₚ. With Nₛ/Nₚ = 10/100, the secondary voltage is Vₛ = 220 × 1/10 = 22 V.
- Series current. This 22 V drives current through 15 kΩ and 7 kΩ in series, a total of 22 kΩ. So I = (22 V)/(22 kΩ) = 1 mA.
V₀ = Vₛ × 7/(15 + 7) = 22 × 7/22 = 7 V
- So. V₀ is taken across the 7 kΩ resistor alone: 1 mA × 7 kΩ = 7 V, which is option (a).
The idea to keep. A transformer only sets the voltage at the secondary. After that it is an ordinary circuit, so use the voltage divider and check which resistor the output is actually taken across.
Answer from the NTA final answer key. Solution by PrepWiser.