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

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#1. 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.

#2. 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.

#3. 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

#4. 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: Using electromagnet, the magnetic field strength further increase by increasing the current. Hence it will enhance the power of electric.

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

aluminum

soft iron

copper

steel

#6. The essential difference between an AC generator and a DC generator is that

AC generator has an electromagnet while a DC generator has permanent magnet.

DC generator will generate a higher voltage.

AC generator will generate a higher voltage.

AC generator has slip rings while the DC generator has a commutator.

#7. The strength of each of magnet reduces to half when it cut along its length into the equal parts magnetic field strength of a solenoid. Polarity of solenoid can be determined by

use of compass needle

Right hand thumb rule

fleming left hand rule

either (a) or (b)

Explanation: (d) both (a) and (b) can be use to determine the polarity of solenoid.

#8. 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.

#9. 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).

#10. 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

#11. The nature of magnetic field line passing through the centre of current carrying circular loop is

circular

ellipse

parabolic

straight line

Explanation:(d) magnetic field line at the centre of current carrying loop appears as a straight line.

#12. 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.

#13. Switches are connected to

live wire

neutral wire

earth wire

any one

#14. Magnetic effect of current was discovered by

Oersted

Faraday

Bohr

Ampere

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

#15. To convert an AC generator into DC generator

Split ring type commutator must be used

Slip rings and brushes must be used

A stronger magnetic field has to be used

A rectangular wire loop has to be used

Explanation: AC generator has slip rings while the DC generator has a split ring type commutator. To convert an AC generator into DC generator the split ring type commutator with which unidirectional current is obtained.

#16. 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.

#17. A fuse should always be placed in the

Live wire of the main circuit

Neutral wire of the main circuit

Earth wire of the main circuit

Both live and neutral wire of the main circuit.

#18. 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.

#19. 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.

#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. 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. Overloading is due to

Insulation of wire is damaged

fault in the appliances

accidental hike in supply voltage

All of the other 3 Answers

Explanation: All are the causes to occur overloading

#23. 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.

#24. Which of the following diagrams correctly shows the magnetic field produced by a current- carrying wire?

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

Reduces substantially.

Does not change.

Increases heavily.

Vary continuously.

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