The magnetic field at a perpendicular distance of 2 cm from an infinite straight current carrying conductor is 2x10^-6 T. The current in the wire is

1

(a)

0.1 A

(b)

0.2 A

(c)

0.4 A

(d)

0.8 A

Current carrying wire produces

1

(a)

Only electric field

(b)

Only magnetic field

(c)

Both electric and magnetic field

(d)

None of the above

A circular coil of n turns and radius r carries a current I. The magnetic field at the centre is 

1

(a)

\(\frac { { \mu }_{ o }nI }{ r } \)

(b)

\(\frac { { \mu }_{ o }nI }{ 2r } \)

(c)

\(\frac { { 2\mu }_{ o }nI }{ r } \)

(d)

\(\frac { { \mu }_{ o }nI }{ 4r } \)

A circular coil carrying current behaves as a

1

(a)

bar magnet

(b)

horse shoe magnet

(c)

magnetic shell

(d)

solenoid

A long solenoid has n turns per metre and current I A is flowing through it. The magnetic field induction at the ends of the solenoid is 

1

(a)

zero

(b)

\({ \mu }_{ o }nI/2\)

(c)

\({ \mu }_{ o }nI\)

(d)

\(2{ \mu }_{ o }NI\)

A current carrying circular loop of radius R is placed in the x-y plane with centre at the origin. Half of the loop with x>0 is now bent so that it now lies in the y-z plane.

1

(a)

The magnitude of magnetic moment now diminishes

(b)

The magnetic moment does not change 

(c)

The magnitude of \(\overset { \rightarrow }{ B } \) at (0,0,z), z>>R increases.

(d)

The magnitude \(\overset { \rightarrow }{ B } \) at (0,0,z), z>>R is unchanged.

An electron is projected with uniform velocity along the axis of a current carrying long solenoid. Which of the following is true?

1

(a)

The electron will be accelerated along the axis

(b)

The electron path will be circular about the axis.

(c)

The electron will experience a force at \(45°\) to the axis and hence execute a helical path.

(d)

The electron will continue to move with uniform velocity along the axis of the solenoid.

A circular current loop of magnetic moment M is in arbitrary orientation in an external magnetic field. \(\overset { \rightarrow }{ B } \) The work does to rotate the loop by \(30°\) about an axis perpendicular to its plane is

1

(a)

MB

(b)

\(\sqrt { 3 } \frac { MB }{ 2 } \)

(c)

\(\frac { MB }{ 2 } \)

(d)

zero

An electron moving in a circular orbit of radius r makes n rotations per second. The magnetic field produced at the centre has magnitude

1

(a)

zero

(b)

\(\frac { { \mu }_{ 0 }{ n }^{ 2 }e }{ r } \)

(c)

\(\frac { { \mu }_{ 0 }{ n }e }{ 2r } \)

(d)

\(\frac { { \mu }_{ 0 }{ n }e }{ 2\pi r } \)

Two similar coils of radius R, are lying concentrically with their planes at right angles to each other. The currents flowing in them are I and 2 I respectively. The resultant magnetic field at the centre will be :

1

(a)

\(\frac { \sqrt { 5 } { \mu }_{ 0 }I }{ 2R } \)

(b)

\(\frac { 3{ \mu }_{ 0 }I }{ 2R } \)

(c)

\(\frac { { \mu }_{ 0 }I }{ 2R } \)

(d)

\(\frac { { \mu }_{ 0 }I }{ R } \)

An electron moving with a velocity of 10⁷ ms^-1 enters a uniform magnetic field of 1 T, along a direction parallel to the field. What would be its trajectory?

1

(a)

Straight line.

Explain, how moving charge is a source of magnetic field.

1

(a)

A moving charge produces an electric current which in turns causes the magnetic field.

What are the dimensions of \({ \mu }_{ o }/4\pi \) ?

1

(a)

[M¹L¹T^-2A^-2].

Name the physical quantity whose unit is tesla. Hence define a tesla.

1

(a)

Tesla is the SI unit of magnetic field induction or magnetic flux density at a point in the magnetic field. The magnetic field induction at a point in a magnetic field is said to be 1 tesla if one-coulomb charge while moving with a velocity of 1 m/s, perpendicular to the magnetic field experiences a force of 1 N at that point.

Suppose a helical spring is suspended from the roof of a room and very small weight is attached to its lower end what will happen to the spring when a current is passed through it?Give reason to support your answer?

1

(a)

Spring Will Contract due to the magnetic field produced by the turns of the coil and the weights will be lifted up

Out of Voltmeter and Millivoltmeter, which has the higher resistance?

1

(a)

We know the resistance connected to galvanometer to Convert it into voltmeter is R  - (V/Ig) - G
So if R is higher, range of V will also be higher, so a Voltmeter has the higher resistance.

Proton is moving along the axis of a solenoid carrying current of 2 A and 50 number of turns per unit length. What will be the force acting on the particle

1

(a)

As the magnetic field produced by solenoid is always along its axis, so direction of velocity of proton is along the direction of field, therefore
F = qvB Sin 0 = 0

Out of Ammeter and Milliammeter, which has the higher resistance?

1

(a)

We know the resistance connected to galvanometer to convert it into ammeter is S =(Ig/( I – Ig))xG 
So for higher resistance, the range of I should be small, therefore milliammeter has the higher resistance.

Can a Moving Coil Galvanometer can be used to detect an A.C. in a circuit .Give reason

1

(a)

As MCG detect only the average value of Curent and the average value of AC for a complete cycle is zero.Therefore MCG can not detect AC in a circuit

Two wires of equal length are bent in the form of two loops. One loop is square whereas the other is circular. These are suspended in same magnetic field and same current is passed through them. Explain with reason which will experience greater torque?

1

(a)

For  a given length , the circle has the greatest area , as
\(\tau \) = NIAB 
i.e. torque is proportional to area, so circular current loop experiences the greater torque