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

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

Generator.

Galvanometer.

Ammeter.

Motor.

#2. 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.

#3. 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

#4. 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.

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

Orsted

Fleming

Einstein

Maxwell

#6. For a current in a long straight solenoid N-pole and S-pole are created at the two ends. Among the following statements, the incorrect statement is

The field lines inside the solenoid are in the form of straight lines which indicates that the magnetic field is the same at all points inside the solenoid.

The strong magnetic field produced inside the solenoid can be used to magnetise a piece of magnetic material like soft iron, when placed inside the coil.

The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet.

The N-pole and S-pole exchange position when the direction of current through the solenoid is reversed.

Explanation: A solenoid behaves like a bar magnet. Hence the pattern of magnetic field associated with solenoid and around the bar magnet is same.

#7. Inside the magnet, the field lines moves

from north to south

from south the north

away from south pole

away from north pole

Explanation:
(a) Magnetic field inside the magnet moves from south to north pole.

#8. 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.

#9. An electric generator actually acts as

a source of electric charge.

a source of heat energy.

an electromagnet.

a converter of energy.

#10. 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.

#11. 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.

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

will become zero.

will increase.

will decrease.

will remain unaffected.

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

0 Hz

50 Hz

100 Hz

200 Hz

#14. An induced emf is produced when a magnet is moved into a coil. The magnitude of induced emf does not depend on:

The speed with which the magnet is moved

The number of turns of the coil

The resistivity of the wire of the coil

The strength of the magnet

#15. An electric motor is a device which transforms

Mechanical energy into electrical energy

Electrical energy into mechanical energy

Kinetic energy into potential energy

Electrical energy into Potential energy

#16. The factors on which one magnetic field strength produced by current carrying solenoids depends are

Magnitude of current

Number of turns

Nature of core material

All of the other 3 answers

Explanation: (d) Factors shown in (a), (b) and (c).

#17. 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

#18. Which of the following factors affect the strength of force experience by a current carrying conduct in a uniform magnetic field?

magnetic field strength

magnitude of current in a conductor

length of the conductor within magnetic field

All of the other 3 Answers.

Explanation: (d) All the factors affect the strength of magnetic force.

#19. 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

#20. Commercial electric motors do not use

An electromagnet to rotate the armature

Effectively large number of turns of conducting wire in the current carrying coil

A permanent magnet to rotate the armature

A soft iron core on which the coil is wound

Explanation: An electric motor is a device that converts electric energy into mechanical energy.

An electric motor has an electromagnet in instead of permanent magnet (as permanent magnet does not produce strong magnetic field).

Large number of turns of the conducting wire in the current-carrying coil to produce stronger magnetic field.

It also has a soft iron core on which the coil is wound also known as armature.

#21. Magnetic effect of current was discovered by

Oersted

Faraday

Bohr

Ampere

Explanation: (a) Oersted showed that electricity and magnetism were related phenomena.

#22. A D.C generator works on the principle of

ohm's law

Joule’s law of heating

faraday’s law of electromagnetic induction.

none of the above

Explanation: electric generator works on the basis of electromagnetic induction.

#23. 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

#24. The pattern of the magnetic field produced by the straight current carrying conducting wire is

in the direction opposite to the current

in the direction parallel to the wire

circular around the wire

in the same direction of current

Explanation:(c) Magnetic field line around a current carrying straight conductor is represented by concentric circles.

#25. The direction of induced current is given by

Fleming’s right hand rule.

Fleming’s left hand rule.

Right hand thumb rule.

Left hand thumb rule.

Finish