Resistor Questions

What is a Resistor?

A resistor is an electrical component that regulates the flow of current in an electronic circuit. Reducing the current flow and lowering the voltage in any specific portion of the circuit are the main functions of a resistor. The outer part of the resistor is glazed with insulating paint, and inside, it is made up of copper wires wound around a ceramic rod.

The carbon-composition resistor is the most common type in electronic devices in which fine grainy carbon such as graphite is hardened by mixing it with clay. The proportion of carbon to clay is altered accordingly; if the ratio of carbon to clay is higher, then the resistance will be lower. Another type is known as a wire-wound resistor, in which the element like nichrome wire is wound on an insulating form for manufacturing resistors. This type of resistor can handle higher currents compared to a carbon-composition resistor of a similar physical size.

Combination of Resistances

1. Resistors in Series: When the current flows through all the resistors, then the resistors are said to be in series and are the same.

Resistors in Series Formula – R_eq = R1 + R2 + R3 + ……….. + Rn

2. Resistors in Parallel

When the terminals of resistors are linked to the two same nodes, then the resistors are said to be in parallel. At their terminals, resistors in parallel share the same voltage.

Resistors in Parallel Formula – R_eq = 1/R1 + 1/R2 + 1/ R3 + ………… + 1/Rn

Important Questions on Resistors

1) What happens to the current across each resistor, in a series connection?

a) Current increases

b) Current decreases

c) Current remains the same

d) First increases and then decreases

Correct Option: (c)

Explanation: The current passing through each of the resistors is the same when the resistors are linked in series, and the current is passed through them. The reason behind it is that the resistors are linked end to end, and thus, there is only one route for the current to flow through.

2) Which among the following combinations is not a series connection?

a) Domestic appliances

b) Resistance box

c) Decorative bulbs

d) Electric fuses

Correct Option: (a)

Explanation: In a house, the domestic appliances are connected in parallel combinations, not in series. The reason behind this arrangement is that each of the appliances can be independently switched on and off, which is important in a house’s wiring.

3) As compared to the smallest parallel resistor, the equivalent resistance is much smaller.

a) True

b) False

Correct Option: (a)

Explanation: The above statement is true because, in parallel combination, the overall equivalent resistance is: R_p = 1/R1+1/R2+1/R3. Thus, according to this formula, the final value attained is less than the original value when the inverse of a resistance value is taken. So, as compared to the smallest parallel resistor, the overall equivalent resistance is much smaller.

4) Here are some statements about parallel combinations of resistors; pick the correct one out.

a) The current is the same across the resistors

b) Same resistance is offered by all resistors

c) Across each resistor, the potential difference is the same

d) As compared to the largest resistor, the overall equivalent resistance is higher

Correct Option: (c)

Explanation: The resistors are linked together at both ends in a parallel combination. Therefore, across the resistors, the potential difference will not change and thus, remains the same.

5) Two wires having their radii in ratio 6:3, but the same length and same material are combined in series. Calculate the total resistance of the combination where the resistance of the thicker wire is 18 ohms.

a) 54

b) 44

c) 22

d) 20

Correct Option: (a)

Explanation: The given ratio of radii = 6:3; R2/R1=6/3 → R2 = (2) R1

R1 = 18 ohms (given);

R2 = (2) × 18 = 36 ohms.

Therefore, R1 = 18 ohms and R2 = 36 ohms.

Since they are combined in series, the total resistance (R) = R1 + R2

= 18 + 36

= 54 ohms

Thus, the total resistance of the combination is 54 ohms.

6) In which among the following combinations batteries are generally installed or connected?

a) Parallel

b) Series

c) Both series and parallel

d) None of these

Correct Option: (b)

Explanation: Batteries are generally linked in series because the voltages add up in series combination.

7) The total resistance is superior to the largest resistance in the _____ circuit.

a) Parallel

b) Series

c) Both series and parallel

d) None of these

Correct Option: (b)

Explanation: The total resistance in a series circuit is the sum of all the resistance in the circuit; hence the total resistance is superior to the largest resistance in the circuit.

8) The total resistance is lesser than the smallest resistance in the _____ circuit.

a) Parallel

b) Series

c) Both series and parallel

d) None of these

Correct Option: (a)

Explanation: The equivalent resistance in a parallel circuit is given by (1/sum of the reciprocals of all the resistances) in the circuit. Hence, in the circuit, it is less than the smallest resistance.

9) Which among the following variety of resistors are widely used as commercial resistors?

a) Ultrasonic resistor

b) Zinc resistor

c) Copper resistor

d) Wire-wound resistor

Correct Option: (d)

Explanation: Wire-wound resistors are made by winding the wires of alloys like manganin. Also, these are electrically reflexive components that limit current and are comparatively impervious to temperature.

10) What is a Resistor?

An electrical component that bounds or regulates the flow of current in an electronic circuit is a resistor. For an active device such as a transistor, the resistor can also be used to deliver a definite voltage.

Practice Questions

1) What is a resistor?

2) What are the series and parallel combinations in resistors?

3) Define resistivity.

4) What is Ohm’s law?

5) What are the applications of resistors?

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