## In the given circuit, connect a nichrome wire of length ‘L’ between points X and Y and note the ammeter reading Answer any four questions from (a) to (e).

## Question 3 (a)

## When this experiment is repeated by inserting another nichrome wire of the same thickness but twice the length (2L), what changes are observed in the ammeter reading?

## (i) Ammeter reading will increase

## (ii) Ammeter reading will decrease

## (iii) Will show double the increase

## (iv) No change in ammeter reading

**
Answer:
**

Resistance is directly proportional to length of the conductor.

So, if
**
length is increased
**
,
**
resistance increases
**
.

If resistance increases,
**
current decreases
**
.

Therefore, the
**
ammeter reading
**
will
**
decrease.
**

So, the
**
correct answer is (ii).
**

## Question 3 (b)

## State the changes that are observed in the ammeter reading if we double the area of crosssection without changing the length in the above experiment.

## (i) Ammeter reading will increase

## (ii) Ammeter reading will decrease

## (iii) Will decrease half

## (iv) No change in ammeter reading

**
Answer:
**

Resistance of a conductor is inversely proportional to area of cross section.

So, if the
**
area of the cross section increases
**
,
**
resistance decreases.
**

If resistance decreases,
**
current increases
**
.

Therefore, the
**
ammeter reading
**
will
**
increase.
**

So, the
**
correct answer is (i).
**

## Question 3 (c)

## In a circuit two resistors of 5 Ω and 10 Ω are connected in series. Compare the current passing through the two resistors.

## (i) 1: 2

## (ii) 1: 3

## (iii) 2: 1

## (iv) 1:1

**
Answer:
**

In a
**
series connection
**
of resistors, the
**
same current passes through all the resistors.
**

Hence, the
**
current will be the same.
**

So, Ratio of the currents will be
**
1: 1
**
.

So, the
**
correct answer is (iv).
**

## Question 3 (d)

## The instrument used to measure current is ____________.

## (i) Ammeter

## (ii) Voltmeter

## (iii) Galvanometer

## (iv) manometer

**
Answer:
**

An instrument that measures electric current in a circuit is an
**
Ammeter.
**

So, the
**
correct answer is (i).
**

## Question 3 (e)

## When nichrome and copper wire of same length and same radius are connected in series and current I is passed through them. Which wire gets heated up more?

## (i) Nichrome wire

## (ii) Copper wire

## (iii) Both will heat up at the same temperature

## (iv) None of the wire will get heated up.

**
Answer:
**

Heat produced, H = I
^{
2
}
R

Where,

- I is the current
- R is the resistance

In a series circuit, the same current passes through both the wires.

So, Heat produced is directly proportional to the resistance.

For the same length and same radius, the
**
resistance of nichrome wire
**
is
**
more
**
than copper wire due to its higher resistivity.

Hence,
**
Nichrome wire
**
is
**
heated up more
**
than copper wire.

So, the
**
correct answer is (i).
**

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