NEET (UG)

Practice Test 1 — Alternating Current

12 questions • 18 minutes • auto-graded with full solutions

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Section A — MCQ (Single Correct)

Question 1

The rms value of an AC of peak $I_0$ is:

Solution: $I_{rms} = I_0/\sqrt{2}$.

Question 2

The reactance of a capacitor is:

Solution: $X_C = 1/\omega C$.

Question 3

In a pure capacitor, the current:

Solution: Current leads the voltage by $90^{\circ}$.

Question 4

The impedance of a series LCR circuit is minimum at:

Solution: $Z = R$ (minimum) at resonance.

Question 5

The resonant angular frequency is:

Solution: $\omega_0 = 1/\sqrt{LC}$.

Question 6

The power factor of a pure inductor is:

Solution: $\cos90^{\circ} = 0$ — wattless.

Question 7

A transformer with twice as many secondary turns as primary doubles the:

Solution: $V_s/V_p = N_s/N_p = 2$.

Question 8

For an ideal transformer, the input and output powers are:

Solution: $V_p I_p = V_s I_s$ (energy conserved).

Section B — Assertion & Reason

Question 9

A: The mains voltage rated $220\ \text{V}$ has a peak value greater than $220\ \text{V}$.
R: The quoted mains voltage is the rms value, which is $V_0/\sqrt{2}$.

Solution: Since $220$ V is rms, the peak is $220\sqrt{2} \approx 311$ V — R explains A.

Question 10

A: An ideal inductor consumes no average power from an AC source.
R: The current in a pure inductor is $90^{\circ}$ out of phase with the voltage.

Solution: The $90^{\circ}$ phase gives $\cos\phi = 0$, hence zero average power — R explains A.

Question 11

A: A transformer can step up or step down a steady DC voltage.
R: A transformer operates on the principle of mutual induction.

Solution: A transformer needs changing flux, so it does not work on DC — A is false; R correctly states it uses mutual induction.

Question 12

A: Electrical power is transmitted over long distances at high voltage.
R: At higher voltage the current is lower, reducing $I^{2}R$ losses in the lines.

Solution: Lower current at high voltage cuts line losses — R explains A.