Class 10 Science · Original EZT practice
Magnetic Effects of Electric Current (Class 10 Chapter 12): summary and practice
A current-carrying wire deflects a compass needle - that single observation opens this chapter. It builds the magnetic field around conductors, the rules for finding directions, the solenoid, the force on a conductor, and finishes inside your home wiring. All questions are original EZT tutor practice following the chapter's own section order.
8 original worked examples, 8 fresh self-check questions and 4 mixed questions, with explained answers. These are not copied textbook exercises, an official chapter index or a full answer key. No affiliation with NCERT is claimed.
Official sources for topic and edition context, checked 20 October 2026:
1. Magnetic field and field lines
A magnetic field is the region where a magnet or current exerts force. Field lines are closed curves that never cross; outside a magnet they run from the north pole to the south pole, and closer lines mean a stronger field.
2. Field due to current-carrying conductors
A straight conductor gives concentric circular field lines - the right-hand thumb rule gives their direction. A circular loop concentrates the field at its centre, and a solenoid produces a uniform field inside and a bar-magnet-like field outside.
3. Force on a conductor in a magnetic field
A current-carrying conductor in a magnetic field experiences a force. Its direction depends on the current direction and the field direction, and Fleming's left-hand rule gives it: first finger field, second finger current, thumb motion.
4. Domestic electric circuits
Homes receive 220 V at 50 Hz through live (red), neutral (black) and earth (green) wires. The 5 A circuit runs bulbs and fans; the 15 A circuit runs geysers and coolers. The fuse protects against overcurrent, and earthing carries fault current safely away.
Choose, solve, check, then try a fresh question.
Before calculating, read the method prompt and name the condition that makes it useful. Write your own attempt. Open the steps only when you need them, and use the check to catch a wrong sign, unit or interpretation. Finish with the fresh question before reading its answer.
Read the compass-needle experiment
Choose the method: A deflected compass needle is evidence of a magnetic field from the current.
EZT practice question
A straight wire carrying current is held over a compass needle. What happens, and what does it show?
Show the worked solution
- The needle deflects when the current flows.
- A magnetic needle moves only in a magnetic field.
Answer: The needle deflects, showing that the current produces a magnetic field around the wire.
Check: Reversing the current reverses the deflection - the field direction follows the current direction.
Watch for this: Do not say the wire attracts the needle; the needle turns because of the field, not a pull on its mass.
Now try it yourself
What happens to the deflection if the current is increased?
Check your answer
It increases.
A larger current gives a stronger magnetic field.
State the properties of field lines
Choose the method: Four facts: closed curves, no crossings, direction, density.
EZT practice question
List the properties of magnetic field lines.
Show the worked solution
- They are closed curves running from north to south outside the magnet.
- No two field lines cross.
- Where lines crowd, the field is stronger.
Answer: Field lines are closed non-crossing curves, directed north to south outside the magnet, with crowded lines marking stronger field.
Check: If two lines crossed, the field would point two ways at one point - impossible.
Watch for this: Do not draw field lines starting or ending in empty space; they are closed loops.
Now try it yourself
What does the spacing of field lines tell you?
Check your answer
How strong the field is; closer lines mean a stronger field.
Field strength shows up as line density.
Apply the right-hand thumb rule
Choose the method: Thumb along the current; curled fingers give the field direction.
EZT practice question
Current flows upward through a vertical wire. What is the direction of the magnetic field around it?
Show the worked solution
- Grip the wire with the right hand, thumb pointing along the current (upward).
- The curled fingers show the field direction.
Answer: The field lines are concentric circles, running anticlockwise when seen from above.
Check: Reverse the current to downward and the field reverses to clockwise from above.
Watch for this: Do not use the left hand; the rule is defined for the right hand.
Now try it yourself
Current flows from east to west in a horizontal wire. What is the field direction at a point below the wire?
Check your answer
Toward the south (apply the thumb rule: thumb west, fingers curl from north over the top to south below).
The curled fingers below the wire point south when the thumb points west.
Describe the solenoid field
Choose the method: Inside is uniform; outside matches a bar magnet.
EZT practice question
Describe the magnetic field of a current-carrying solenoid, inside and outside.
Show the worked solution
- Inside, the field lines are parallel and evenly spaced - a uniform field.
- Outside, the pattern matches a bar magnet, with one end behaving as north and the other as south.
Answer: Uniform field inside; bar-magnet-like field outside, with north and south ends.
Check: Reversing the current swaps the north and south ends, as the field direction follows the current.
Watch for this: Do not say the field inside is strongest at the ends; inside the solenoid it is uniform.
Now try it yourself
How can you strengthen a solenoid's field?
Check your answer
Increase the current or the number of turns, or insert a soft iron core.
Each change raises the field the turns produce together.
Find the force direction with Fleming's left-hand rule
Choose the method: First finger field, second finger current, thumb motion - all at right angles.
EZT practice question
A conductor carries current eastward in a magnetic field pointing north. What is the direction of the force on it?
Show the worked solution
- Hold the left hand with first finger north (field) and second finger east (current).
- The thumb then points upward.
Answer: The force acts vertically upward.
Check: Reversing either the current or the field reverses the force; reversing both leaves it unchanged.
Watch for this: Do not use the right hand here; force on a conductor uses the left hand.
Now try it yourself
When is the force on a current-carrying conductor in a magnetic field zero?
Check your answer
When the current is parallel to the field.
The force is largest at right angles and vanishes when the two align.
Find the current an appliance draws
Choose the method: I = P/V at the domestic supply of 220 V.
EZT practice question
A 60 W bulb runs on the 220 V mains. What current does it draw, and can it go on the 5 A circuit?
Show the worked solution
- I = P/V = 60/220.
- That is about 0.27 A, far below 5 A.
Answer: About 0.27 A - easily within the 5 A circuit.
Check: A 5 A circuit at 220 V supports up to 1100 W, and 60 W is far inside that.
Watch for this: Do not divide 220 by 60; current is power over voltage.
Now try it yourself
What current does a 1000 W heater draw at 220 V?
Check your answer
About 4.55 A.
I = 1000/220 = 4.55 A.
Choose between the 5 A and 15 A circuits
Choose the method: Compute the current and match it to the circuit rating.
EZT practice question
A 1500 W geyser runs on the 220 V mains. Which circuit does it need, 5 A or 15 A?
Show the worked solution
- I = P/V = 1500/220, about 6.82 A.
- That exceeds 5 A but is well inside 15 A.
Answer: About 6.82 A, so it needs the 15 A circuit.
Check: High-power heating appliances (geysers, coolers) are exactly what the 15 A line is for.
Watch for this: Do not put a 6.82 A load on the 5 A line; the fuse would keep blowing.
Now try it yourself
A 750 W iron draws how much current, and which circuit?
Check your answer
About 3.41 A, so the 5 A circuit is enough.
I = 750/220 = 3.41 A, under 5 A.
Find the maximum load on a domestic circuit
Choose the method: P = V x I at 220 V for each rating.
EZT practice question
What is the maximum power a 5 A circuit and a 15 A circuit can supply at 220 V?
Show the worked solution
- P = V x I.
- For 5 A: 220 x 5 = 1100 W. For 15 A: 220 x 15 = 3300 W.
Answer: 1100 W on the 5 A circuit and 3300 W on the 15 A circuit.
Check: This is why lights and fans share one line while geysers get their own.
Watch for this: Do not add the two ratings; each circuit is protected by its own fuse.
Now try it yourself
Which wire carries fault current safely to the ground?
Check your answer
The earth wire (green insulation).
Earthing keeps metal bodies from staying live during a fault.
Try a mixed set
Choose a method or explanation before opening each answer.
1. Domestic supply voltage and frequency in India?
Show answer and reason
220 V at 50 Hz.
Both values appear in every domestic-circuit calculation.
2. Wire colours: live, neutral, earth?
Show answer and reason
Red, black and green.
Colour coding keeps wiring safe and consistent.
3. What does the fuse do?
Show answer and reason
It melts and breaks the circuit when the current exceeds its rating.
That protects appliances and wiring from overcurrent.
4. State the right-hand thumb rule.
Show answer and reason
Grip the conductor with the right hand, thumb along the current; the curled fingers give the field direction.
It fixes the field direction around a straight conductor.
Try it yourself
Work these on paper before checking any notes. Answers are deliberately not shown here.
- A 1000 W heater runs on 220 V. What current does it draw?
- A 750 W iron runs on 220 V. What current does it draw, and which circuit does it belong on?
- State the maximum power a 5 A circuit can supply at 220 V.
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Questions about this practice page
- Why does a house have an earth wire?
- Earthing carries fault current safely into the ground, so a live metal body cannot shock you.
- What does the fuse do?
- It is a thin wire that melts and breaks the circuit when the current crosses its rating, protecting the wiring and appliances.
- How do you find the direction of the magnetic field around a straight wire?
- With the right-hand thumb rule: thumb along the current, and the curled fingers show the circular field direction.
- Why are there two circuits, 5 A and 15 A?
- Low-power loads like bulbs and fans go on the 5 A line; high-power heating appliances like geysers draw more than 5 A and need the 15 A line.
- Are these the NCERT exercise questions for Magnetic Effects of Electric Current (Class 10)?
- No. EZT pages are original practice following the chapter's section order - use them to prepare for the textbook exercises, not as a substitute for your book.