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6.

The increase  in energy of a metal bar of length L and  cross-sectional area A when   compressed with a load M along its length is (where, Y= Young's modulus of the material of metal bar )

A) $\frac{FL}{2 AY}$

B) $\frac{F^{2}L}{2 AY}$

C) $\frac{F^{}L}{2AY}$

D) $\frac{F^{2}L^{2}}{2 AY}$

7.

Two metal wires P and Q  of same length and material are stretched  by same load. Their masses are in the ratio  m1 : m2 . The ratio of elongations of wire  P to that of Q is

A) $m_1^2:m_2^2$

B) $m_2^2:m_1^2$

C) $m_2:m_1$

D) $m_1:m_2$

8.

Heat energy is incident on the surface at the rate of 1000 J/min.if the coefficient of absorption is 0.8 and the coefficient of reflection is  0.1, then  heat energy transmitted by the surface in 5  min is

A) 100 J

B) 500 J

C) 700 J

D) 900 J

9.

A series combination of N1 capacitors (each of capacity C1)  is charged to potential difference 3 V. Another parallel combination of N2 capacitors  (each of capacity C2) is charged to potential difference V. The total energy stored in both the combinations is same. The value of C1  in terms of C2 is

A) $\frac{C_{2}N_{1}N_{2}}{9}$

B) $\frac{C_{2}N_{1}^{2}N_{2}^{2}}{9}$

C) $\frac{C_{2}N_{1}}{9N_{2}}$

D) $\frac{C_{2}N_{2}}{9N_{1}}$

10.

The deflection  in  galvanometer falls to $\left(\frac{1}{4}\right)^{th}$  when it is shunted by 3 $\Omega$ .If additional shunt of 2 $\Omega$ is connected to earlier shunt in parallel, the deflection in galvanometer falls to

A) $\frac{1}{2}$

B) $\left(\frac{1}{3}\right)^{th}$

C) $\left(\frac{1}{4}\right)^{th}$

D) $\left(\frac{1}{8.5}\right)^{th}$

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