The resistance of a wire is $20 \Omega$. It is stretched, so that the length becomes three times, then the new resistance of the wire will be

In a meter bridge the resistances $R$ and $S$ are such that the null point is found at a distance of 40 cm from one end. If a resistance of $10 \Omega$ is connected in parallel with shunt $S$, then the null point occurs at 90 cm from the same end. The values of the two resistances $R$ and $S$ respectively are

Two similar coils which are separated by 2 m having radius of 1 m and number of turns 80 have a common axis. Calculate the strength of magnetic field at a point midway between them on their common axis when a current is 0.2 A .

A particle of mass $m$ and charge $Q$ moving with a speed $v$ in a circular path of radius $R$ has magnetic moment $\mu$. If the mass of the particle is doubled and maintains the same speed while revolving in the same circular path, then the magnetic moment will be