1. Find the current in the circuit.
a) 1 A
b) 2 A
c) 3 A
d) 4 A
Explanation: I=V/R. Total resistance R = 20+40=60ohm. V=120V. I=120/60=2A.
2. In a series circuit, which of the parameters remain constant across all circuit elements such as resistor, capacitor and inductor etcetera?
a) Voltage
b) Current
c) Both voltage and current
d) Neither voltage nor current
Explanation: In a series circuit, the current across all elements remain the same and the total voltage of the circuit is the sum of the voltages across all the elements.
3. Voltage across the 60ohm resistor is______
a) 72V
b) 0V
c) 48V
d) 120V
Explanation: The 60ohm resistance is shorted since current always choses the low resistance path. Voltage across short circuit is equal to zero, hence voltage across the resistor is 0.
4. Find the voltage across the 6 ohm resistor.
a) 150V
b) 181.6V
c) 27.27V
d) 54.48V
Explanation: Total current I=150/(6+12+15)=(150/33)V.
V across 6 ohm = 6*I = 6*(150/33)V = 27.27V.
5. If there are two bulbs connected in series and one blows out, what happens to the other bulb?
a) The other bulb continues to glow with the same brightness
b) The other bulb stops glowing
c) The other bulb glows with increased brightness
d) The other bulb also burns out
Explanation: Since the two bulbs are connected in series, if the first bulb burns out there is a break in the circuit and hence the second bulb does not glow.
6. What is the value of x if the current in the circuit is 5A?
a) 15 ohm
b) 25 ohm
c) 55 ohm
d) 75 ohm
Explanation: Total voltage=sum of voltages across each resistor. =>150=10*5+5*5+5*x. Solving the equation, we get x=15 ohm.
7. A voltage across a series resistor circuit is proportional to?
a) The amount of time the circuit was on for
b) The value of the resistance itself
c) The value of the other resistances in the circuit
d) The power in the circuit
Explanation: V=IR hence the voltage across a series resistor circuit is proportional to the value of the resistance.
8. Many resistors connected in series will?
a) Divide the voltage proportionally among all the resistors
b) Divide the current proportionally
c) Increase the source voltage in proportion to the values of the resistors
d) Reduce the power to zero
Explanation: In a series circuit, the current remains the same across all resistors hence the voltage divides proportionally among all resistors.
9. What is the voltage measured across a series short?
a) Infinite
b) Zero
c) The value of the source voltage
d) Null
Explanation: A short is just a wire. The potential difference between two points of a wire is zero hence the voltage measured is equal to zero.
10. What happens to the current in the series circuit if the resistance is doubled?
a) It becomes half its original value
b) It becomes double its original value
c) It becomes zero
d) It becomes infinity
Explanation: I=V/R. If R becomes 2R then I becomes I/2 i.e. half of its original value.