Two coaxial solenoids of different radii carry current I  in the same direction. Let F1 be the magnetic force on the inner solenoid due to the outer one and F2 be the magnetic force  on the outer solenoid due to the inner one, Then,

A) $F_{1}=F_{2}=0$

B) $F_{1}$ is radially inwards and $F_{2}$ is radially outwards

C) $F_{1}$ is radially inwards and $F_{2}$=0

D) $F_{1}$ is radially outwards and $F_{2}$=0


In the circuit  shown below, the current in the 1Ω resistor is 


A) 1.3 A, from P to Q

B) 0 A

C) 0.13 A , from Q to P

D) 0.13 A , from P to Q


When 5V  potential difference is applied across a wire of length 0.1m  the drift speed of electrons is  $2.5\times 10^{-4}ms^{-1}$. If the electron density in the wire is  $8\times 10^{28}m^{-3}$  the resistivity of the material is close to Ωm

A) $1.6\times 10^{8}$ Om

B) $1.6\times 10^{7}$ Om

C) $1.6\times 10^{6}$ Om

D) $1.6\times 10^{-5}$ Om


A uniformly charged solid sphere of radius R has potential V0 (measured with respect to ∞) on its surface. For this sphere, the equipotential sufaces,  with potentials  $\frac{3V_{0}}{2},\frac{5V_{0}}{4},\frac{3V_{0}}{4} and \frac{V_{0}}{4}$ have radius R1, R2 ,R3  and R4  respectively. Then   R4

A) $R_{1}=0$ and $R_{2} > (R_{4}-R_{3})$

B) $R_{1}\neq0 and( R_{2}-R_{1})-(R_{4}-R_{3})$

C) $R_{1}=0$ and $R_{2} < (R_{4}-R_{3})$

D) 2R< $R_{4} $


A train moving on a straight track with speed 20 ms-1. It is blowing its whistle at the frequency of 1000Hz. The percentage change in the frequency heard by a person standing near the track as the train passes him is  close to (speed of sound =320 ms-1  )

A) 6%

B) 12%

C) 18%

D) 24%