Physics

Problem

The ends

Q

and

R

of two thin wires,

PQ

and

RS

, are soldered (joined) together. Initially each of the wires has a length of

1 \text{ m}

10^\circ\text{C}

. Now the end

P

is maintained at

10^\circ\text{C}

, while the end

S

is heated and maintained at

400^\circ\text{C}

. The system is thermally insulated from its surroundings. If the thermal conductivity of wire

PQ

is twice that of the wire

RS

and the coefficient of linear thermal expansion of

PQ

1.2 \times 10^{-5} \text{ K}^{-1}

, the change in length of the wire

PQ

is (a)

0.78 \text{ mm}

(b)

0.90 \text{ mm}

(c)

1.56 \text{ mm}

(d)

2.34 \text{ mm}

(Advanced 2016)