NEET Alternating Currents — Set 17

Question 1

A transformer has $ N_p = 250 $, $ N_s = 500 $. If $ V_s = 440 \, \text{V} $ (rms), what is the primary voltage?

Accepted Answer

$ \frac{V_s}{V_p} = \frac{N_s}{N_p} $. $ V_p = V_s \times \frac{N_p}{N_s} = 440 \times \frac{250}{500} = 220 \, \text{V} $.

Question 2

A series LCR circuit has $ R = 30 \, \Omega $, $ X_L = 45 \, \Omega $, $ X_C = 15 \, \Omega $. What is the power factor?

Accepted Answer

$ Z = \sqrt{R^2 + (X_L - X_C)^2} = \sqrt{30^2 + (45 - 15)^2} = \sqrt{900 + 900} = \sqrt{1800} \approx 42.43 \, \Omega $. Power factor: $ \cos \phi = \frac{R}{Z} = \frac{30}{42.43} \approx 0.707 $.

Question 3

What is the effect on an ideal transformer’s secondary voltage if the number of turns in the secondary coil is halved?

Accepted Answer

In an ideal transformer, $ \frac{V_s}{V_p} = \frac{N_s}{N_p} $. If the number of secondary turns ($ N_s $) is halved, the secondary voltage ($ V_s $) becomes half its original value, assuming primary voltage ($ V_p $) remains constant.

NEET Physics: Alternating Currents — Practice Set 17

Q1. A transformer has \( N_p = 250 \), \( N_s = 500 \). If \( V_s = 440 \, \text{V} \) (rms), what is the primary voltage?

Q2. A series LCR circuit has \( R = 30 \, \Omega \), \( X_L = 45 \, \Omega \), \( X_C = 15 \, \Omega \). What is the power factor?

Q3. What is the effect on an ideal transformer’s secondary voltage if the number of turns in the secondary coil is halved?

Q4. A \( 40 \, \Omega \) resistor is connected to a \( 120 \, \text{V} \) (rms) AC source. What is the rms current?

Q5. A transformer has \( N_p = 200 \), \( N_s = 400 \). If \( V_p = 110 \, \text{V} \) (rms), what is the secondary voltage?

Q6. A transformer has \( N_p = 300 \), \( N_s = 150 \). If \( V_p = 240 \, \text{V} \) (rms), what is the secondary voltage?

Q7. A \( 11 \, \mu\text{F} \) capacitor is connected to a \( 110 \, \text{V} \), \( 60 \, \text{Hz} \) source. What is the capacitive reactance?

Q8. In an AC circuit with a resistor and inductor in series, what determines the magnitude of the phase difference between voltage and current?

Q9. A \( 25 \, \mu\text{F} \) capacitor is connected to a \( 230 \, \text{V} \), \( 50 \, \text{Hz} \) AC source. What is the peak current?

Q10. A \( 6 \, \mu\text{F} \) capacitor is connected to a \( 220 \, \text{V} \), \( 50 \, \text{Hz} \) source. What is the capacitive reactance?