R4RIN – MCQs, Mock Tests | ECAT ECAT Physics Electromagnetism MCQs

Magnetic force acting on a unit positive charge moving perpendicular to the magnetic field with a unit velocity is called

1. magnetic flux
2. magnetic field intensity
3. magnetic induction
4. self inductance

✅ Correct Answer: 3

A current carrying conductor is placed in a uniform magnetic field parallel to it. The magnetic force experienced by the conductor is

1. F=1/B
2. F=1/Bsin?
3. F/0
4. F=1/Bcos?

✅ Correct Answer: 3

What is the value of the current in a wire of 10cm long at the right angle to a uniform magnetic field of 0.5 Weber/m2 when the force acting on the wire is 5N?

1. 1A
2. 10A
3. 100A
4. 1000A

✅ Correct Answer: 3

When a particle of charge q and mass m enters into a uniform magnetic field B moving with a velocity v perpendicular to the direction for the field it describes a circular path of radius

1. R=qB/mV
2. R=mV/qB
3. R=qmV/B
4. R=qmB/V

✅ Correct Answer: 2

Two parallel wires carrying currents in the opposite directions

1. repel each other
2. attract each other
3. have no effect upon each other
4. they cancel out their individual magnetic fields

✅ Correct Answer: 1

A magnetic compass will be deflected if it is kept near a

1. charge in motion
2. charge at rest
3. both
4. none

✅ Correct Answer: 1

A magnetic field

1. always exerts a force on a charged particle
2. never exerts a force on a charged particles
3. exerts a force if the charged particle is moving in the direction of the magnetic field lines
4. exerts a force if the charged particle is moving perpendicular to the magnetic field lines

✅ Correct Answer: 4

A moving coil galvanometer of resistance 100? gives half scale deflection for a current of 20mA. What will be the potential difference across it?

1. 4 volt
2. 5 volt
3. 2 volt
4. 0.4 volt

✅ Correct Answer: 3

Which one of the following material is most suitable for making core of an electromagnet?

1. air
2. steel
3. Cu-Ni alloy
4. soft iron

✅ Correct Answer: 4

The magnetic force experienced by a charge particle moving in a magnetic field will be minimum when it moves

1. perpendicular to the field
2. parallel to the field
3. inclined parallel to the field
4. at an angle of 45?

✅ Correct Answer: 2

The relationship between Tesla and smaller unit Gauss of magnetic induction is given by

1. 1T = 103 G
2. 1T = 10-4 G
3. 1T = 10-2 G
4. 1T = 104 G

✅ Correct Answer: 4

If the plane of the rectangular coil is parallel to the magnetic field (i.e radial magnetic field) the torque on the coil is

1. ? = NIAB cos?
2. ? = NIAB sin?
3. ? = NIAB tan?
4. ? = NIAB

✅ Correct Answer: 4

Magnetic flux and flux density are related by

1. magnetic flux = flux density / area
2. magnetic flux = flux density x area
3. flux density = magnetic flux area
4. flux density = magnetic flux x area

✅ Correct Answer: 1

The standard vector symbol for flux density is

1. M
2. L
3. H
4. B

✅ Correct Answer: 2

The charged particle enters the uniform magnetic field in such a way that its initial velocity is not perpendicular to the field the orbit will be

1. a circle
2. a spiral
3. an ellipse
4. helix

✅ Correct Answer: 4

An electron enters a region where the electric field E is perpendicular to the magnetic field B. It will suffer no deflection if

1. E = BeV
2. B = eE/V
3. E = BV
4. E = BeV/2

✅ Correct Answer: 4

Value of permeability of tree space in SI units is

1. 4?x10-9 WbA-1m-1
2. 4?x10-7 WbA-1m-1
3. 4?x10-10 WbA-1m-1
4. 4?x10-8 WbA-1m-1

✅ Correct Answer: 3

The magnetic field strength of solenoid is

1. B = ??NI
2. B = ??N/I
3. B = ??nI
4. both (b) and C

✅ Correct Answer: 2

An instrument which can measure potential without drawing any current is

1. voltmeter
2. galvanometer
3. cathode ray oscilloscope (CRO)
4. ammeter

✅ Correct Answer: 3

The deflection for 50 division of galvanometer is decreased to 25 divisions by shunt resistance of 12?. Galvanometer resistance is

1. 18?
2. 30?
3. 24?
4. 12?

✅ Correct Answer: 4

When the coil of the galvanometer is in equilibrium then the deflecting couple is

1. zero
2. equal to the restoring couple
3. greater than the restoring couple
4. smaller than the restoring couple

✅ Correct Answer: 2

The sensitivity of a galvanometer is given by

1. C/BAN
2. CAN/B
3. BAN/C
4. ABC/N

✅ Correct Answer: 1

Which one of the following is not an electromechanical instrument?

1. galvanometer
2. voltmeter
3. ammeter
4. AC transformer and DC generator

✅ Correct Answer: 4

Minimum current required to produce a deflection of 1 mm on a scale at a distance of 1 meter is

1. 0.1 A
2. 1:00 AM
3. current sensitivity
4. 1 m A

✅ Correct Answer: 3

In a multi range ammeter as the range increases

1. shunt value decreases
2. shunt value increases
3. shunt value remains the same
4. none of the above

✅ Correct Answer: 1

While measuring the unknown resistance the help of slide wire bridge a greatest accuracy can be achieved when

1. a most sensitive galvanometer is used
2. a steady voltage cell is used
3. the balance point is close to the middle of the wire
4. a high resistance box is used in one of its gap

✅ Correct Answer: 3

A sensitive galvanometer gives full-scale deflection with 100 mV. If the resistance of the galvanometer is 50? the maximum current that can flow through safely is

1. 2.0 mA
2. 20 mA
3. 200 mA
4. 0.2 mA

✅ Correct Answer: 1

An ammeter measures the total current flowing through a circuit when it is connected

1. in series with the circuit
2. in parallel with circuit
3. in series with any of the parallel resistances in the circuit
4. in parallel with any of the series resistances in the circuit

✅ Correct Answer: 1

Coil of a galvanometer is suspended in a radial magnetic field so that the deflecting torque on the coil is always

1. BINA cosa
2. BINA sina
3. BINA tana
4. BINA

✅ Correct Answer: 4

A galvanometer basically is an instrument used to

1. detect current in a circuit
2. measure current flowing through a circuit
3. measure voltage across a circuit
4. measure potential difference between two points in a circuit

✅ Correct Answer: 1

The effective way to increase the sensitivity of a moving coil galvanometer is to

1. use a very long and fine suspension
2. use a coil of very large area
3. use a coil with very large number of turns
4. use a very strong magnetic field

✅ Correct Answer: 4

A wheat stone bridge is said to be balanced when

1. maximum current flows through the galvanometer branch
2. minimum current flows through the galvanometer branch
3. potential difference across galvanometer branch is maximum
4. potential difference across galvanometer branch is zero

✅ Correct Answer: 4

When an electron moving with a uniform speed in a vacuum enters a magnetic field in a direction perpendicular to the field the subsequent path of the electron is

1. a straight line parallel to the field
2. a parabola in a plane perpendicular to the field
3. a circle in a plane perpendicular to the field
4. a straight line along its initial direction

✅ Correct Answer: 3

A particle of mass m charge q and speed V enters a uniform magnetic radius r. The radius r of the circle is

1. independent mass m
2. directly proportional to m
3. directly proportional to q
4. directly proportional to B

✅ Correct Answer: 2

Galvanometer is a very sensitive device with

1. very low damping
2. very high damping
3. no damping at all
4. radial field disintegration

✅ Correct Answer: 1

Which one of the following methods would be able to increase the sensitivity of a moving coil galvanometer ?

1. connect a shunt across the coil
2. use a coil of smaller cross sectional area
3. use a coil having less number of turns
4. use spiral springs whose force constant is small

✅ Correct Answer: 4

Heating a magnet will

1. weaken it
2. strengthen it
3. reverse its polarity
4. demagnetize it completely

✅ Correct Answer: 1

If a current carrying solenoid is suspended freely it will

1. be rotating
2. come to rest in N-S direction
3. vibrating like galvanometer needle
4. comes to rest after rotation

✅ Correct Answer: 2