Magnetic Effects of Electric Current — Class 10 MCQs with Answers

Magnetic Effects of Electric Current — important questions & MCQs with answers (Class 10 Science (Physics))

6 solved questions from this chapter's difficulty levels, each with its answer and explanation. Tap an option to check yourself.

0 of 6 answered

1. Q1 of 6Easy

   First scientist to observe magnetic effect of current:

   AFaradayBMaxwellCOerstedDAmpere
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   Answer: Oersted

   Explanation: Hans Oersted (1820) noticed deflection of compass near current-carrying wire.

2. Q2 of 6Easy

   Magnetic field lines:

   ARun from S to N outside the magnetBCross each other near the polesCRun from N to S outside and S to N inside the magnetDStart at N and end at S without entering the magnet
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   Answer: Run from N to S outside and S to N inside the magnet

   Explanation: A magnet's field lines form closed loops: they run from the north pole to the south pole outside the magnet and continue from south back to north inside it, never crossing or stopping midway.

3. Q3 of 6Medium

   Current flows northward in a horizontal wire, shown end-on in the figure. The magnetic field at P, directly above the wire, is:

   

   AWestBEastCUpDDown
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   Answer: East

   Explanation: By the right-hand thumb rule, point the thumb north along the current and the curled fingers give the field's direction; directly above the wire that curl points east, not west or straight up.

4. Q4 of 6Medium

   Assertion (A): The magnetic field inside a long current-carrying solenoid is the same at all points. Reason (R): The field lines inside a current-carrying solenoid are concentric circles.

   ABoth A and R are true and R is the correct explanation of ABBoth A and R are true but R is not the correct explanation of ACA is true but R is falseDA is false but R is true
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   Answer: A is true but R is false

   Explanation: A is true: the field inside a solenoid is uniform. R is false: the field lines inside a solenoid are parallel straight lines; concentric circles form around a straight wire.

5. Q5 of 6Hard

   Front face of a solenoid acts as N pole if current at that face flows:

   AAlong the axisBClockwiseCAnticlockwiseDIn either direction
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   Answer: Anticlockwise

   Explanation: Viewed from outside, a solenoid face carrying anticlockwise current is a North pole (the clock rule for poles).

6. Q6 of 6Hard

   Assertion (A): When the direction of current in a rod placed in a magnetic field is reversed, the direction of the force on the rod is also reversed. Reason (R): The force on a current-carrying conductor in a magnetic field is largest when the current is at right angles to the field.

   ABoth A and R are true and R is the correct explanation of ABBoth A and R are true but R is not the correct explanation of ACA is true but R is falseDA is false but R is true
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   Answer: Both A and R are true but R is not the correct explanation of A

   Explanation: Both are true. R is about when the force is largest, not about its direction, so it does not explain why reversing the current reverses the force.

Magnetic Effects of Electric Current notes: key concepts (Class 10 Science (Physics))

A current produces a magnetic field and a changing magnetic field produces a current — the two effects behind the electric motor and the generator. This chapter covers Oersted's discovery, field patterns, the force on a conductor, induction, and the wiring of domestic circuits.

Magnetism and magnetic field

The region around a magnet or current-carrying conductor in which a magnetic force acts; it has both magnitude and direction.

Magnetic field lines

Curves showing the field's direction, running from north to south outside a magnet; they never intersect, since the field has one direction at each point.

Oersted's experiment

Oersted found that a compass needle placed near a current-carrying wire deflects, the first demonstration that electricity produces magnetism.

Field due to a straight conductor

Concentric circles around the wire, becoming weaker with distance and stronger with larger current.

Right-hand thumb rule

Grip the wire with the right hand, thumb along the current; the curled fingers give the direction of the magnetic field.

Field due to a circular loop

Every part of the loop contributes field in the same direction at the centre, so the field there is much stronger than for a straight wire.

Solenoid

A coil of many turns whose field resembles that of a bar magnet, uniform inside, and used to magnetise materials into electromagnets.

Electromagnet

A soft-iron core inside a solenoid, magnetised strongly while current flows and losing magnetism when it stops.

Force on a current-carrying conductor

A conductor carrying current in a magnetic field experiences a force, greatest when current and field are perpendicular.

Fleming's left-hand rule

With the first finger along the field and the second along the current, the thumb gives the direction of the force — the motor rule.

Electric motor

A device converting electrical energy into mechanical energy, using the force on a current-carrying coil and a split-ring commutator to reverse the current each half turn.

Electromagnetic induction

A changing magnetic field across a coil induces a current in it — the effect Faraday discovered and the basis of all generators.

Fleming's right-hand rule

With the thumb along the motion and first finger along the field, the second finger gives the direction of the induced current — the generator rule.

Electric generator

A device converting mechanical energy into electrical energy by rotating a coil in a magnetic field.

AC and DC, and frequency

Alternating current reverses direction periodically — in India 50 times per second, a frequency of 50 Hz — while direct current flows one way only.

Domestic circuits and safety

Live, neutral and earth wires supply the house; the earth wire and fuse together protect against shock and overload.