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

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#1. The main advantage of A.C power transmission over D.C power transmission over’ long distance is

AC transmit without much loss of energy

less insulation problem

less problem of instability

easy transformation.

Explanation: AC transmit over a long distance without much loss of energy as compare to DC.

#2. 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.

#3. By which instrument, the presence of magnetic field be determined?

Magnetic Needle

Ammeter

Galvanometer

Voltmeter

(a) With the help of magnetic field, one can find the presence of magnetic field in a region by observing its deflection.

#4. At the time of short circuit, the current in the circuit

Reduces substantially.

Does not change.

Increases heavily.

Vary continuously.

#5. In electric motor, to make the coil rotating continuously in the same direction, current is reversed in the coil after every half rotation by a device called

carbon brush

commutator

slip ring

armature

Explanation: (b) A device that reverses the direction of current in the arms of armature through a circuit is called commutation.

#6. 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.

#7. A uniform magnetic field exists in the plane of paper pointing from left to right as shown in figure. In the field an electron and a proton move as shown. The electron and the proton experience.

Forces both pointing into the plane of paper

Forces both pointing out of the plane of paper

Forces pointing into the plane of paper and out of the plane of paper, respectively

Force pointing opposite and along the direction of the uniform magnetic field respectively

Explanation: Direction of current is taken as opposite to the flow of electron or in the direction of flow of protons.

In the given figure, the proton and electron are moving in opposite direction to each other and in perpendicular to the direction of magnetic field. So, current due to both electron and proton are in same direction. Hence, the forces acting on both will be in the same direction. By Fleming’s left hand rule the direction, force is pointing into the plane of paper.

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

Orsted

Fleming

Einstein

Maxwell

#9. What should be the core of an electromagnet?

soft iron

hard iron

rusted iron

none of answer

#10. Which of the following correctly describes the magnetic field near a long straight wire?

The field consists of straight lines perpendicular to the wire.

The field consists of straight lines parallel to the wire.

The field consists of radial lines originating from the wire.

The field consists of concentric circles centred on the wire.

#11. If the current values periodically from zero to a maximum value, back to zero and then reverses its direction, the current is

direct

alternative

pulsating

none of the answer

Explanation: The alternating current reverse its direction periodically.

#12. Which device produces the electric current?

generator

galvanometer

ammeter

motor

#13. 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.

#14. The magnetic field lines outside a bar magnet:

Originate from the South pole and end at its North Pole

Originate from the North pole and end at its East Pole

Originate from the North Pole and end at its South Pole

Originate from the South pole and end at its West Pole

#15. A soft iron bar is inserted inside a current-carrying solenoid. The magnetic field inside the solenoid:

Will decrease

Will increase

Will become zero

Will remain the same

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

Generator.

Galvanometer.

Ammeter.

Motor.

#17. 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.

#18. Direction of rotation of a coil in electric motor is determined by

fleming’s right hand rule

fleming’s left hand rule

faraday law of electromagnetic inductors

None of answer

Explanation: (b) Fleming’s left hand rule.

#19. A current carrying conductor is held in exactly vertical direction. In order to produce a clockwise magnetic field around the conductor, the current should be passed in the conductor:

From top to bottom

From left to right

From bottom to top

From right to left

#20. A coil of insulated copper wire is connected to a galvanometer forming a loop and a magnet id. A: Held stationary B: Moved away along its axis C: Moved towards along its axis.There will be a induced current in:

A only

A and B only

B and C only

A, B and C

#21. A soft iron bar is introduced inside the current carrying solenoid. The magnetic field inside the solenoid

will decrease

will remains same

will increase

will become zero

Explanation: (c) Soft iron inside the current carrying solenoid act as an electromagnet.

#22. 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

#23. If the key in the arrangement as shown is taken out (the circuit is made open) and magnetic field lines are drawn over the horizontal plane ABCD, the lines are

Concentric circles

Elliptical in shape

Straight lines parallel to each other

Concentric circles near the point O but of elliptical shapes as we go away from it

Explanation: If key is taken out then current will stop and no magnetic field exists due to the conductor. Therefore, at the point O, there will be earth’s magnetic field and they will be straight lines parallel to each other.

#24. We can induce the current in a coil by

moving the coil in a magnetic field

by changing the magnetic field around it

by changing the orientation of the coil in the magnetic field

All of above

#25. The shape of the magnetic field lines produced by a current carrying conductor are:

Straight lines

Concentric circles

Concentric ellipse

Concentric parabolas

Finish