MCQS | A magnetic field

Question :- A certain stress applied to an elastic material produces a certain strain in it. If the elastic limit is not exceeded the energy gained per unit volume of the material is given by

1.Stress/strain

2.(stress/strain)

3.Stress x strain

4.(Stress / strain)

Question :- 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?

Question :- 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

Question :- A ire of length L is stretched by a length ? when a force F is applied at one end. If the elastic limit is not exceeded the amount of energy stored in the wire is

1.F?

2.(F?)

3.F? 2/L

4.F?2

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

1.charge in motion

2.charge at rest

3.both

4.none

Question :- 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

Question :- 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

Question :- 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

Question :- A rubber cord of cross-sectional area 2cm2 has a length of 1m. When a tensile force of 10N is applied the length of the cord increases by 1cm. What is the youngs modulus of rubber?

1.2x108 Nm-2

2.5x106 Nm-2

3.0.5x10-6 Nm-2

4.0.2x10-6Nm-2

Question :- 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

Question :- A uniform steel wire of length 4m and area of cross-section 3x10-6m2 is extended by 1mm by the application of a force. If the youngs modulus of steel is 2x1011 Nm-2 the energy stored in the wire is

1.0.025J

2.0.50J

3.0.75J

4.0.100J

Question :- 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

Question :- A wire suspended vertically from one end is stretched by attaching a weight of 20N to the lower end. The weight stretches the wire by 1mm. How much energy is gained by the wire?

1.0.01J

2.0.02J

3.0.04J

4.1.0J

Question :- 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

Question :- 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

Question :- An instrument which can measure potential without drawing any current is

1.voltmeter

2.galvanometer

3.cathode ray oscilloscope (CRO)

4.ammeter

Question :- 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

Question :- Galvanometer is a very sensitive device with

1.very low damping

2.very high damping

3.no damping at all

4.radial field disintegration

Question :- Heating a magnet will

1.weaken it

2.strengthen it

3.reverse its polarity

4.demagnetize it completely

Question :- 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

Question :- 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

Question :- 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

Question :- 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

Question :- 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

Question :- 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

Question :- SI unit of flux density is

1.NA-1m-1

2.NAm-1

3.NmA-1

4.NmA-2

Question :- 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

Question :- 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?

Question :- 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

Question :- The figure shown the stress-strain graph of a certain substance. Over which region of the graph is Hooks law obeyed?

1.AB

2.BC

3.CD

4.ED

Question :- The magnetic field strength of solenoid is

1.B = ??NI

2.B = ??N/I

3.B = ??nI

4.both (b) and (c)

Question :- The magnetic force experienced by a charge particle moving in a magnetic field will be minimum when it move

1.perpendicular to the field

2.parallel to the field

3.inclined parallel to the field

4.at an angle of 45?

Question :- 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

Question :- The sensitivity of a galvanometer is given by

1.C/BAN

2.CAN/B

3.BAN/C

4.ABC/N

Question :- The standard vector symbol for flux density is

1.M

2.L

3.H

4.B

Question :- 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

Question :- 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

Question :- What are the dimensions of stress?

1.MLT-2

2.ML-2T-1

3.ML-1T-2

4.ML?T-1

Question :- What is the SI unit of modulus of elasticity of substance?

1.Nm-2

2.Jm-2

3.Nm-1

4.Being a number it has no unit.

Question :- 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

Question :- When a force is applied at one end of an elastic wire it produces at strain ? in the wire. If y is the youngs modulus of the material of the wire the amount of energy stored per unit volume of the wire is given by

1.Y?

2.Y?

3.Y?2

4.Y?2

Question :- 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

Question :- 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

Question :- 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

Question :- Which of the following substances posses the highest elasticity?

1.Rubber

2.Steel

3.Glass

4.Copper

Question :- Which one of the following is not an electromechanical instrument?

1.galvanometer

2.voltmeter

3.ammeter

4.AC transformer and DC generator

Question :- 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

Question :- 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

Question :- Which one of the following physical quantities does not have the dimensions of force per unit area?

1.Stress

2.Strain

3.Youngs modulus

4.Pressure

Question :- 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