A coil of one loop is made from a wire of length L and thereafter a coil of two loops is made from same wire. The ratio of magnetic field at the centre of the coils will be:
1. 1 : 4
2. 1 : 1
3. 1 : 8
4. 4 : 1
A current-carrying coil (I = 5A, R = 10 cm) has 50 turns. The magnetic field at its centre will be:
1. 1.57 mT
2. 3.14 mT
3. 1 mT
4. 2 mT
For the adjoining figure, the magnetic field at a point 'P' will be:
1.
2.
3.
4.
An electron moves in a circular orbit with a uniform speed \(v\). It produces a magnetic field \(B\) at the centre of the circle. The radius of the circle is proportional to:
1. \(\sqrt{\frac{v}{B}}\)
2. \(\frac{v}{B}\)
3. \(\frac{B}{v}\)
4. \(\sqrt{\frac{B}{v}}\)