CBSE X Science Magnetic Effects of Current - EducareHut (Next Gen Knowledge Point)

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#1. A magnetic field directed in north direction acts on an electron moving in east direction. The magnetic force on the electron will act

vertically upwards.

towards east.

vertically downwards.

towards north.

#2. Relative strength of magnetic field at a point in the space surrounding the magnet is shown by the

length of magnet

thickness of magnet

degree of closeness of the field.

resistance offered by the surroundings

(a) The force acting on the pole of another magnet by the crowded magnetic field lines is greater.

#3. The magnetic field is the strongest at

middle of the magnet.

north pole.

south pole.

both poles.

#4. Material of the core of a strong magnet is

aluminum

soft iron

copper

steel

#5. The frequency of electricity produced by DC generator is equal to

0 Hz

50 Hz

100 Hz

200 Hz

#6. Choose the incorrect statement.

Fleming's right hand rule is a simple rule to know the direction of induced current.

The right hand thumb rule is used to find the direction of magnetic fields due to current carrying conductors.

The difference between the direct and alternating currents is that the direct current always flows in one direction, where as the alternating current reverses its direction periodically.

In India, the AC changes direction after every1/50 second.

Explanation: Here option (a), (b) and (c) are knowledge based options and are correct.

Option (d) is incorrect because the frequency of ‘AC’ in India is 50 cycle/s. So, time period of AC is 1/50 s. We know that, AC changes its direction after every half time period, i.e., 1/ (2 × 50) or1/100 s. So, in India the AC changes direction after every 1/100 s.

#7. The condition for the phenomena of electromagnetic induction is that there must be a relative motion between

the galvanometer and magnet

the coil of wire and galvanometer

the coil of wire and magnet

the magnet and galvanometer

Explanation: (c) The relative motion between the magnet and coil of wire causes change in magnetic field lines linked with the coil to produces induced current if the circuit is closed.

#8. A current through a horizontal power line flows from south to North direction. The direction of magnetic field line 0.5m above it is

North

South

West

East

Explanation:(a) Apply right-hand thumb rule.

#9. If two circular coils can be arranged in any of the three situations as shown in the diagrams below, then their mutual induction will be:

Maximum in situation a

Maximum in situation b

Maximum in situation c

The same in all situations

#10. Magnetic lines of force inside current carrying solenoid are

perpendicular to axis.

along the axis and are parallel to each other.

parallel inside the solenoid and circular at the ends.

circular.

#11. A.C generator works on the principle of

force experience by a conductor in magnetic field

electromagnetic induction

electrostatic

force experience by a charge particle in electric field.

Explanation: Generator works on principle of electromagnetic induction.

#12. A positive charge is moving upwards in a magnetic field directed towards north. The particle will be deflected towards

west

north

south

east

Explanation: (a) Apply fleming’s left hand rule

#13. Choose the incorrect statement from the following regarding magnetic lines of field

The direction of magnetic field at a point is taken to be the direction in which the North Pole of a magnetic compass needle points

Magnetic field lines are closed curves

If magnetic field lines are parallel and equidistant, they represent zero field strength

Relative strength of magnetic field is shown by the degree of closeness of the field lines

Explanation: Parallel and equidistant magnetic field lines represent uniform and constant field strength.

#14. A positive charge is moving towards a person. The direction of magnetic field lines will be in

Clockwise direction

Anticlockwise direction

Vertically upward direction

Vertically downward direction

#15. The force exerted on a current carrying wire placed in a magnetic field is zero when the angle between wire and the direction of magnetic field is:

45 Degree

60 Degree

90 Degree

180 Degree

#16. Fleming’s left hand and Right hand rules are used in

Generator and electric motor

Electric motor and generator

any rule can be used for any device

both are not applied for generator and motor.

Explanation: Electric motor employs Fleming left hand rule while for generator, Fleming right-hand rule is used.

#17. A circular loop placed in a plane perpendicular to the plane of paper carries a current when the key is ON. The current as seen from points A and B (in the plane of paper and on the axis of the coil) is anti-clockwise and clockwise respectively. The magnetic field lines point from B to A. The N-pole of the resultant magnet is on the face close to (Point A is behind the loop)

A if the current is small and B if the current is large

B if the current is small and A if the current is large

Explanation: When we see from point A, the direction of current will be anticlockwise and when we see the direction of current from point B then it will be clockwise. It means current is flowing as shown in the figure given below.

By right-hand thumb rule, the magnetic field lines will enter from point B and come out from point A.

We also know that, the magnetic field lines emerge from North Pole and merge at the South Pole outside the magnet.

Hence, in this circuit face A represents North pole and face B represents south pole.

#18. The device used for producing electric current is called a

Generator.

Galvanometer.

Ammeter.

Motor.

#19. Switches are connected to

live wire

neutral wire

earth wire

any one

#20. Which among of these are the main characteristics of fuse element?

High conductivity

low melting point

do not burn due to oxidation

All of the other answer

Explanation: Fuse wire must have all the characteristic to prevent from a possible damage.

#21. The strength of magnetic field inside a long current carrying straight solenoid is

More at the ends than at the centre

Minimum in the middle

Same at all points

Found to increase from one end to the other

Explanation: Inside the solenoid, magnetic field lines are parallel to each other hence forming a uniform field strength which indicates that the magnetic field is the same at all points inside the solenoid.

#22. A constant current flows in a horizontal wire in the plane of the paper from east to west as shown in figure. The direction of magnetic field at a point will be north to south.

Directly above the wire

Directly below the wire

At a point located in the plane of the paper on the north side of the wire

At a point located in the plane of the paper on the south side of the wire

Explanation: If we observe the direction of magnetic field by applying right hand thumb rule then, we will find that the direction of magnetic field is from North to South below the wire.

#23. Which of the following statement is not correct about the magnetic field?

Magnetic field lines form a continuous closed curve.

Magnetic field line do not interest each other.

Direction of tangent at any point on the magnetic field line curve gives the direction of magnetic field at that point.

Outside the magnet, magnetic field lines go from South to North pole of the magnet.

Explanation:
(d) Outside the magnet, magnetic field line emerges from North-pole and moves towards south-pole.

#24. Who has stated the Right hand Thumb Rule?

Orsted

Fleming

Einstein

Maxwell

#25. In the arrangement shown in figure, there are two coils wound on a non-conducting cylindrical rod. Initially, the key is not inserted. Then the key is inserted and later removed. Then

The deflection in the galvanometer remains zero throughout

There is a momentary deflection in the galvanometer but it dies out shortly and there is no effect when the key is removed.

There are momentary galvanometers deflections that die out shortly, the deflections are in the same direction.

There are momentary galvanometers deflections that die out shortly, the deflections are in opposite directions. Thus, the galvanometer shows momentary deflections in opposite directions.

Explanation: As the current in the first coil changes, the magnetic field associated with it also changes. Thus the magnetic field lines around the other coil also change. Hence the change in magnetic field lines associated with the secondary coil is the cause of induced electric current in it by the process of electromagnetic induction. Due to this reason, a momentary deflection in galvanometer will be observed which will die out soon when the current flowing through first coil attains steady state.

Due to similar phenomenon, a momentary deflection is again observed in opposite direction when key is removed as in this case current is decreasing in the circuit.

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