Question #01

A plane conducting loop is located in a uniform magnetic field that is directed along the x- axis. For what orientation of the loop is flux a maximum? For what orientation is the flux a minimum?

Answer:

When plane of loop is placed perpendicular to the magnetic filed, the flux will be maximum. When plane of loop is placed parallel to the magnetic field, the flux will be minimum.

Question # 02

A current in a conductor produces a magnetic field, which can be calculated using Ampere’s law. Since current is defined as the rate of flow of charge, what can you conclude about the magnetic field due to stationary charges? What about moving charges?

Answer:

Magnetic field due to stationary charges is zero. Moving charges produce magnetic field around them.

Question# 03

Why is B non. zero outside a solenoid?

Answer:

The magnetic lines of force are widely spaced outside the solenoid and produce weak magnetic field but not  be zero.

Question # 04:

Describe the change in the magnetic field inside a solenoid carrying a steady current I, if 

(a) the length of the solenoid is double but the number of turns remains the same.

(b) The number o turns is double, but the length remains the same.

Answer: 

The magnetic field for the solenoid is given by,

B = unI —-> 1

where n = N/l = no.of turns per unit length.

(a) If the length (l) of the solenoid is doubled but no.of turns N remains the same. Then

n’ = N/2l =1/2n, The no.of turns per unit^2 length become half. Hence magnetic field decreases to half.

(b) If the no.of turns is doubled but the length remains the same. Then n’ = 2N/l = 2(N/l) = 2n. The no.of  turns per unit length become double. Hence magnetic field  increases to two times.

Question# 5

At a given instant, a proton moves in the positive X direction in a region where there is magnetic field in the negative Z direction. What is the direction of the magnetic force? Will the proton continue to move in the positive X direction? Explain.

Answer

 If proton moves along +x axis and magnetic field is along -z axis then according to R.H rule, F = q (V XB), the magnetic force on it will be along +y – axis and it will start to move in circular path in xy plan around – z – axis and will not continue to move in the + x – direction.

Question # 6

Two charged particles are projected into a region where there is a magnetic field perpendicular to their velocities. If the charges are deflected in opposite directions, what can you say about them?

Answer:

Two charged particles are projected in a magnetic field perpendicular to their velocities and they are deflected in opposite directions. The particles will be oppositely charged.

Question # 7

Suppose that a charge q is moving in a uniform magnetic field with a velocity V. Why is there no work done by the magnetic force that acts on  the charge q?

Answer:

A charge q is moving in a uniform magnetic field B, with a velocity V adopts a circular path due to magnetic force. The angle between magnetic force and displacement (velocity) will be 90. Then 

work = F. d = Fd Cos 90 = Fd (0) = 0.

Hence no work will be done.

 

Question # 8

If a charged particle moves in a straight line through some region of space, can you say that the magnetic field in the region is zero?

Answer:

No, when a charge particle moves in a straight line in the direction of magnetic filed then force acting on it will be zero. 

F = qVB Sin 0 = qVB (0) = 0

Hence, we can not say that the magnetic field in that region is zero.

Question # 9

Why does the picture on a TV screen become distorted when a magnet is brought near the screen?

Answer:

 The picture on a TV screen is formed due to electrons. When a magnet is brought near the TV screen the electron beam is distorted due to magnetic force,

F = eVB Sin theta

on each electron.

Question # 10

Is it possible to orient a current loop in a uniform magnetic field such that the loop will not tend to rotate? Explain.

Answer:

When the current carrying loop is placed in a uniform magnetic field the torque acting on it is given by

T = NIAB Cos alpha

Where  Alpha is the angle between B and plane of loop. If Alpha = 90 and Cos 90 = 0

Then,

T = 0

This gives if the plane of the loop is oriented at 90 with B then loop will not tend to rotate.

Question # 11

How can a current loop be used to determine the presence of a magnetic filed in a given region of space?

Answer:

When  a current carrying loop is placed in the presence of a magnetic field with its plan makes an angle Alpha with B. The torque acting on it will be, 

T = NIAB Cos Alpha

If the current loop deflects field is present otherwise not.

 Question # 12

How van you use a magnetic field to separate isotopes of chemical element?

 Answer:

When isotopes of chemical element are projected in a magnetic field at right angle then magnetic force, F = eVB provide them centerpetal force, 

F = mv^2/ r

=> eVB = mv^2/r

=> r = mv/eB

Isotopes have same charge, but due to different masses they adopt different places and separated.

Question # 13

What should be thee orientation of a current carrying coil in a magnetic field so that torque acting upon the coil is

(a) maximum

(b) minimum.

Answer:

When a current carrying loop is placed in a uniform magnetic field the torque acting on it is given by 

  T = NIAB Cos Alpha.

 Where Alpha is the angle between B and plane of the coil.

 (a) when plane of the coil is oriented parallel to B. Then,

 alpha = 0 and cos 0 = 1 and T = NIAB (1) = NIAB (max). Torque will be max.

 (b) When plane of the coil is oriented at right angle to B. Then

 Alpha = 90 and Cos 90 = 0, T = NIAB (0) = 0

 Torque will be minimum.

 Question # 14

Why the resistance of an ammeter should be very low?

Answer

Ammeter is always connected in series The magnitude of current decrease through the circuit with the presence of ammeter. To measure maximum current the resistance of ammeter should be very small as compared to the resistance of circuit.

Question # 15

Why the voltmeter should have a very high resistance?

Answer:

Voltmeter is always connected in parallel with the two points where potential is to be measured. The potential across the points decrease with presence of voltmeter because it draws some current Iv of the voltmeter, the resistance of voltmeter should be large as compared to the resistance of the circuit.