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

1.	\(1.2 \times 10^{-5}\) T, towards north
2.	\(2.1 \times 10^{-5}\) T, towards south
3.	\(1.2 \times 10^{-5}\) T, towards south
4.	\(2.1 \times 10^{-5}\) T, towards north

A long straight wire in the horizontal plane carries a current of 50 A in the north to south direction. The magnitude and direction of the magnetic field at a point 2.5 m east of the wire is:
1. \(4 \times 10^{-6}~ T\) vertically upward
2. \(4 \times 10^{-6} ~T\) vertically downward
3. \(3 \times 10^{-6} ~T\) vertically upward
4. \(3 \times 10^{-6} ~T\) vertically downward

A long straight wire carries a current of \(35~\text{A}.\) The magnitude of the magnetic field at a point \(20~\text{cm}\) from the wire is:
1. \(3.5 \times 10^{-6} ~\text T\)
2. \(3.5 \times 10^{-5} ~\text T\)
3. \(4.5 \times 10^{-6} ~\text T\)
4. \(4.5 \times 10^{-5} ~\text T\)

A straight horizontal conducting rod of length \(0.45~\text m\) and mass \(60 ~\text {gm}\) is suspended by two vertical wires at its ends. A current of \(5.0 ~\text A\) is set up in the rod through the wires. What magnetic field should be set up normally to the conductor in order that the tension in the wires is zero?
1. \(0.13 ~\text T\)
2. \(0.06 ~\text T\)
3. \(0.26 ~\text T\)
4. \(0.18 ~\text T\)

The wires that connect the battery of an automobile to its starting motor carry a current of \(300~\text{A}\) (for a short time). What is the force per unit length between the wires if they are \(70~\text{cm}\) long and \(1.5~\text{cm}\) apart?
1. \(2.2~\text{N/m}\)
2. \(4.7~\text{N/m}\)
3. \(3.2~\text{N/m}\)
4. \(1.2~\text{N/m}\)

A uniform magnetic field of 1.5 T exists in a cylindrical region of a radius of 10.0 cm, its direction parallel to its axis along east to west. A wire carrying a current of 7.0 A in the north to south direction passes through this region. What is the magnitude and direction of the force on the wire if the wire intersects the axis?

1. 3.4 N vertically upward direction.
2. 2.1 N vertically upward direction.
3. 3.4 N vertically downward direction.
4. 2.1 N vertically downward direction.

A circular coil of \(20\) turns and a radius of \(10~\text{cm}\) is placed in a uniform magnetic field of \(0.10~\text{T}\) normal to the plane of the coil. If the current in the coil is \(5.0~\text{A},\) what is the total torque on the coil?
1. \(1.0~\text{N-m}\)
2. \(\text{zero}\)
3. \(0.5~\text{N-m}\)
4. \(0.3~\text{N-m}\)

A galvanometer coil has a resistance of 15 Ω and the metre shows full-scale deflection for a current of 4 mA. How will you convert the metre into an ammeter of range 0 to 6 A?

A galvanometer coil has a resistance of \(12 ~\Omega\) and the metre shows full-scale deflection for a current of \(3 ~\text{mA}.\) How will you convert the metre into a voltmeter of range \(0\) to \(18 ~\text{V}?\)

A solenoid 60 cm long and of radius 4.0 cm has 3 layers of windings of 300 turns each. A 2.0 cm long wire of mass 2.5 g lies inside the solenoid (near its centre) normal to its axis; both the wire and the axis of the solenoid are in the horizontal plane. The wire is connected through two leads parallel to the axis of the solenoid to an external battery which supplies a current of 6.0 A in the wire. What value of current (with an appropriate sense of circulation) in the windings of the solenoid can support the weight of the wire? $\left(g=9.8<mspace\; width="1em"></mspace>m<mspace\; width="1em"></mspace>s^{-2}\right)$

1. 106 A
2. 108 A
3. 100 A
4. 110 A