3
MCQ (Single Correct Answer)
When a voltage measuring device is connected to $A C$ mains, the meter shows the steady input voltage of 220 V . This means
A
input voltage cannot be $A C$ voltage, but a DC voltage
B
maximum input voltage is 220 V
C
the meter reads not $v$ but $< v^2>$ and is calibrated to read $\sqrt{< v^2>}$
D
the pointer of the meter is stuck by some mechanical defect
4
MCQ (Single Correct Answer)
To reduce the resonant frequency in an $L-C-R$ series circuit with a generator
A
the generator frequency should be reduced
B
another capacitor should be added in parallel to the first
C
the iron core of the inductor should be removed
D
dielectric in the capacitor should be removed
5
MCQ (Single Correct Answer)
Which of the following combinations should be selected for better tuning of an $L-C-R$ circuit used for communication?
A
$R=20 \Omega, L=1.5 \mathrm{H}, C=35 \propto \mathrm{~F}$
B
$R=25 \Omega, L=2.5 \mathrm{H}, C=45 \alpha \mathrm{~F}$
C
$R=15 \Omega, L=3.5 \mathrm{H}, C=30 \alpha \mathrm{~F}$
D
$R=25 \Omega, L=1.5 \mathrm{H}, C=45 \propto \mathrm{~F}$
6
MCQ (Single Correct Answer)
An inductor of reactance $1 \Omega$ and a resistor of $2 \Omega$ are connected in series to the terminals of a 6 V (rms) AC source. The power dissipated in the circuit is
A
8 W
B
12 W
C
14.4 W
D
18 W
7
MCQ (Single Correct Answer)
The output of a step-down transformer is measured to be 24 V when connected to a 12 W light bulb. The value of the peak current is
A
$1 / \sqrt{2} \mathrm{~A}$
B
$\sqrt{2} \mathrm{~A}$
C
2 A
D
$2 \sqrt{2} \mathrm{~A}$