A long straight wire carries a current of 35 A. What is the magnitude of the field $B$ at a point 20 cm from the wire?

A square coil of side 10 cm consists of 20 turns and carries a current of 12 A. The coil is suspended vertically and the normal to the plane of the coil makes an angle of $30^{\circ}$ with the direction of a uniform horizontal magnetic field of magnitude 0.80 T. What is the magnitude of torque experienced by the coil?

In a chamber, a uniform magnetic field of 6.5 G (1 G = $10^{-4}$ T) is maintained. An electron is shot into the field with a speed of $4.8 \times 10^6 m s^{-1}$ normal to the field. Explain why the path of the electron is a circle. Determine the radius of the circular orbit. ($e = 1.5 \times 10^{-19}$ C, $m_e = 9.1\times 10^{-31}$ kg), obtain the frequency of revolution of the electron in its circular orbit. Does the answer depend on the speed of the electron? Explain.

In a chamber, a uniform magnetic field of 6.5 G (1 G = $10^{-4}$ T) is maintained. An electron is shot into the field with a speed of $4.8 \times 10^6 m s^{-1}$ normal to the field. Explain why the path of the electron is a circle. Determine the radius of the circular orbit. ($e = 1.5 \times 10^{-19}$ C, $m_e = 9.1\times 10^{-31}$ kg)

Two long and parallel straight wires A and B carrying currents of 8.0 A and 5.0 A in the same direction are separated by a distance of 4.0 cm. Estimate the force on a 10 cm section of wire A.

A 3.0 cm wire carrying a current of 10 A is placed inside a solenoid perpendicular to its axis. The magnetic field inside the solenoid is given to be 0.27 T. What is the magnetic force on the wire?

Two moving coil meters, $M_1$ and $M_2$ have the following particulars: $R_1 = 10 \Omega$, $N_1 = 30$, $A_1 = 3.6 \times 10^{-3} m^2$, $B_1 = 0.25$ T; $R_2 = 14 \Omega$, $N_2 = 42$, $A_2 = 1.8 \times 10^{-3} m^2$, $B_2 = 0.50$ T (The spring constants are identical for the two meters). Determine the ratio of (a) current sensitivity of $M_2$ and $M_1$.

A circular coil of wire consisting of 100 turns, each of radius 8.0 cm carries a current of 0.40 A. What is the magnitude of the magnetic field $B$ at the centre of the coil?

Two moving coil meters, $M_1$ and $M_2$ have the following particulars: $R_1 = 10 \Omega$, $N_1 = 30$, $A_1 = 3.6 \times 10^{-3} m^2$, $B_1 = 0.25$ T; $R_2 = 14 \Omega$, $N_2 = 42$, $A_2 = 1.8 \times 10^{-3} m^2$, $B_2 = 0.50$ T (The spring constants are identical for the two meters). Determine the ratio of (b) voltage sensitivity of $M_2$ and $M_1$.

(a) A circular coil of 30 turns and radius 8.0 cm carrying a current of 6.0 A is suspended vertically in a uniform horizontal magnetic field of magnitude 1.0 T. The field lines make an angle of $60^{\circ}$ with the normal of the coil. Calculate the magnitude of the counter torque that must be applied to prevent the coil from turning.

A long straight wire in the horizontal plane carries a current of 50 A in north to south direction. Give the magnitude and direction of $B$ at a point 2.5 m east of the wire.

(b) Would your answer change, if the circular coil in (a) were replaced by a planar coil of some irregular shape that encloses the same area? (All other particulars are also unaltered.)

What is the magnitude of magnetic force per unit length on a wire carrying a current of 8 A and making an angle of $30^{\circ}$ with the direction of a uniform magnetic field of 0.15 T?

A horizontal overhead power line carries a current of 90 A in east to west direction. What is the magnitude and direction of the magnetic field due to the current 1.5 m below the line?

A closely wound solenoid 80 cm long has 5 layers of windings of 400 turns each. The diameter of the solenoid is 1.8 cm. If the current carried is 8.0 A, estimate the magnitude of $B$ inside the solenoid near its centre.