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Very Short Question and Answers - Resistance of a System of Resistors

Q 1.
Why do we combine resistors in a circuit?

Ans:

We combine resistors to obtain a required total or 'effective' resistance that may not be available as a single resistor and to control the current and voltage in different parts of the circuit.

Q 2.
Define the series combination of resistors.

Ans:

A series combination is when resistors are connected end-to-end so that the same current flows through each resistor.

Q 3.
What is the formula for calculating the total resistance in a series circuit with three resistors R1, R2, and R3?

Ans:

The total resistance R = R1 + R2 + R3.

Q 4.
What happens to the total resistance when resistors are connected in series?

Ans:

The total resistance increases; it is the sum of the individual resistances.

Q 5.
A series circuit has three resistors of values 2 Ω, 3 Ω, and 5 Ω. What is their total resistance?

Ans:

Total resistance = 2 Ω + 3 Ω + 5 Ω = 10 Ω.

Q 6.
How does current flow in a series circuit?

Ans:

The same current flows through all resistors in a series circuit.

Q 7.
What is the effect on the whole circuit if one resistor fails in a series connection?

Ans:

If one resistor fails (breaks) in series, the circuit is broken and the current stops; all devices connected in series go off.

Q 8.
Define parallel combination of resistors.

Ans:

Resistors are in parallel if they are connected such that both ends are joined at the same two points, making the voltage across each resistor the same.

Q 9.
State the formula for total resistance when three resistors R1, R2, and R3 are connected in parallel.

Ans:

1/R = 1/R1 + 1/R2 + 1/R3.

Q 10.
How does the total resistance of parallel combination compare to the smallest individual resistor value?

Ans:

The total resistance in parallel is always less than the smallest resistance of the resistors used.

Q 11.
If two 4 Ω resistors are connected in parallel, what is the resultant resistance?

Ans:

1/R = 1/4 + 1/4 = 2/4 = 1/2, so R = 2 Ω.

Q 12.
How is current distributed in a parallel circuit?

Ans:

The total current divides among the parallel branches according to the resistance of each branch.

Q 13.
If three resistors of 2 Ω, 3 Ω, and 6 Ω are connected in parallel, what is the total resistance?

Ans:

1/R = 1/2 + 1/3 + 1/6 = 3/6 + 2/6 + 1/6 = 6/6 = 1, so total resistance R = 1 Ω.

Q 14.
What is the voltage across each resistor in a parallel arrangement if connected to a battery of 6V?

Ans:

The voltage across each resistor is 6V; all resistors in parallel have the same voltage across them.

Q 15.
Give an example of where series connection of resistors is used in daily life.

Ans:

Festoon lights or serial decorative bulbs are examples; if one bulb fails, the whole string turns off.

Q 16.
Give an example of parallel connection in household wiring.

Ans:

Electrical sockets and home appliances are connected in parallel so that each receives the same voltage and can function independently.

Q 17.
When is it preferable to use resistors in series?

Ans:

Use series combination to increase total resistance or to decrease current in a circuit.

Q 18.
When is it preferable to use resistors in parallel?

Ans:

Use parallel combination to decrease resistance, obtain a higher current, or to provide the same voltage to each device.

Q 19.
What happens if one resistor burns out in a parallel circuit?

Ans:

Only that branch stops working; current continues in the other branches, so the rest of the circuit keeps operating.

Q 20.
Summarise the key differences between series and parallel combinations regarding current and voltage.

Ans:

In series: current is same through all resistors, voltage divides. In parallel: voltage is same across all resistors, current divides.

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