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

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#1. For a current in a long straight solenoid, N and S-poles 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 and S-poles exchange position when the direction of current through the solenoid is reversed

Explanation: Option (a), (b) and (d) are correct. Only option (c) is incorrect because the pattern of magnetic fields due to solenoid and bar magnet is almost same.

#2. The north pole of Earth’s magnet is in the:

Geographical South

Geographical East

Geographical West

Geographical North

#3. 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.

#4. 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.

#5. 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.

#6. 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.

#7. 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.

#8. When current is parallel to magnetic field, then force experience by the current carrying conductor placed in uniform magnetic field is

Twice to that when angle is 60°

Thrice to that when angle is 60°

zero

infinite

Explanation: (a) If the current direction is parallel to the magnetic field, then there will no force on the conductor exerted by the magnetic field.

#9. A magnet is moved towards a coil (i) quickly (ii) slowly. The induced potential difference

#10. The most important safety method used for protecting home appliances from short circuiting or overloading is

Earthing

Use of fuse

Use of stabilizers

Use of electric meter

Explanation: Use of electric fuse is the most important method used for protecting home appliances from short-circuiting or overloading.

Generally, thin wire with low melting having specific rating is connected in series with the electric devices. When the current passing through the fuse exceeds a specific value then by heating effect of current it melts and breaks the circuit.

#11. 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.

#12. 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.

#13. 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).

#14. 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.

#15. The magnetic field is the strongest at

middle of the magnet.

north pole.

south pole.

both poles.

#16. The magnetic field lines always begin from

N-pole and end on S-pole.

S-pole and end on N-pole.

start from the middle and end at N-pole.

start from the middle and end at S-pole.

#17. 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.

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

Generator.

Galvanometer.

Ammeter.

Motor.

#19. The best material to make permanent magnets is

aluminium

soft iron

copper

alnico

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

#21. 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.

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

0 Hz

50 Hz

100 Hz

200 Hz

#23. 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.

#24. 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

#25. 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.

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