21. The correct expression for the instantaneous current if the instantaneous voltage is Vm(sint) in a resistive circuit is?
A. 1A
B. 2A
C. 3A
D. 4A
Answer: B
We know that: V = Vm(sint)
Since i = V/R,
we can write, i = Vm(sint)/R.
22. Calculate the resistance in the circuit if the RMS voltage is 20V and the RMS current is 2A.
A. 2 ohm
B. 5 ohm
C. 10 ohm
D. 20 ohm
Answer: C
We know that:
R = V/I
Substituting the given values from the question, we get R = 10 ohm.
23. The correct expression for the instantaneous current in a resistive circuit is?
A. i = Vm(sint)/R
B. i = Vm(cost)/R
C. i = V(sint)/R
D. i = V(cost)/R
Answer: A
The instantaneous voltage can be written in terms of the maximum voltage in the following manner:
v = Vm(sint)
Since i = v/R
we can write, i = Vm(sint)/R.
24. Can ohm’s law be applied in an ac circuit?
A. Yes
B. No
C. Depends on the RMS’s current
D. Depends on the RMS voltage
Answer: A
Ohm’s law can be applied in ac as well as dc circuits. It can be applied in ac circuits because the condition V = IR holds true even in ac circuits.
25. The correct expression for the instantaneous current if instantaneous voltage is Vm(sint) in an inductive circuit is?
A. i = Vm(sint)/XL
B. i = Vm(cost)/XL
C. i = -Vm(sint)/XL
D. i = -Vm(cost)/XL
Answer: D
V = Vm × sint
I = V/XL = -Vm(cost)/XL (since current lags voltage by 900 in inductive circuit).
26. Inductor does not allow sudden changes in?
A. Voltage
B. Current
C. Resistance
D. Inductance
Answer: B
The inductor does not allow sudden changes in current because if current changes in the inductor occur in zero time, the voltage becomes zero which is not possible.
27. Inductance is __________ to number of turns in the coil.
A. directly proportional
B. inversely proportional
C. equal
D. not related
Answer: A
L = µ0N2A/l
Inductance is directly proportional to the number of turns in the coil.
28. Choke involve use of _____________
A. Resistor
B. Capacitor
C. Inductor
D. Transistor
Answer: C
Choke is a type of coil so it involves the use of an inductor. Capacitors cannot be used in choke coil.
29. What is the value of current in an inductive circuit when there is no applied voltage?
A. Minimum
B. Maximum
C. Zero
D. Cannot be determined
Answer: B
The current in an inductive circuit is maximum when there is no voltage applied because of the coils of the inductor store electric flux.
30. What is the current in an inductive circuit when the applied voltage is maximum?
A. Infinity
B. Maximum
C. Zero
D. Cannot be determined
Answer: C
The current in an inductive circuit is zero or minimum when the value of the applied voltage is maximum.
