CBSE Class 10 Science • Magnetism and Electric Circuits
Magnetic Effects of Electric Current Class 10 Worksheet
Why does a compass needle deflect near a current-carrying wire? How does a solenoid behave like a magnet? Practise these concepts with the Magnetic Effects of Electric Current Class 10 worksheet. Revise magnetic field patterns, direction rules, force on a conductor, AC and DC, and domestic circuits.
This chapter connects electric current with magnetic fields and their effects. Many questions ask you to predict what happens when current is reversed, identify a field direction or explain the purpose of a circuit component. Clear diagrams and careful use of direction rules make these questions easier to solve.
Begin with our Magnetic Effects of Electric Current Class 10 notes and mind map . Then attempt the worksheet independently. The revision notes, practice examples and answers below help you check your reasoning before a chapter test.
Magnetic Effects of Electric Current Class 10 Summary
Magnetic Field and Field Lines
A magnetic field describes the magnetic influence around a magnet or current-carrying conductor. A compass helps identify its direction: the north-seeking end points along the local field. Field lines provide a visual representation of the field.
- Outside a bar magnet, field lines run from north to south.
- Inside the magnet, they return from south to north, forming closed curves.
- The tangent to a field line indicates the field direction.
- Closer field lines represent a stronger field in a standard diagram.
- Field lines do not cross because a non-zero field has one direction at a point.
Field Lines Are a Representation
Magnetic field lines are not physical threads. They show the direction and relative strength of a field. Iron filings can reveal a pattern, while a compass helps establish its direction.
Magnetic Field Around a Straight Conductor
A current-carrying straight wire produces a magnetic field whose lines form concentric circles around the wire. For the same arrangement, increasing current strengthens the field. Moving farther from the wire weakens it.
Right-Hand Thumb Rule
Imagine holding the conductor in your right hand with your thumb pointing along conventional current. Your curled fingers indicate the direction of the magnetic field around the wire.
Worked Example: Current Through the Page
Current towards the observer: represent it with a dot, like an arrow tip. The field is anticlockwise as viewed by the observer.
Current away from the observer: represent it with a cross, like an arrow’s tail. The field is clockwise.
Reversing the current reverses the field direction. Always state the viewing direction when using clockwise or anticlockwise.
Magnetic Field Due to a Circular Coil
Different portions of a current-carrying circular loop contribute to its magnetic field. At the centre, these contributions act along the loop’s axis. Increasing current strengthens the field. Increasing the number of similar turns also strengthens the field when the current and geometry remain unchanged.
Identify the Face of a Coil
Viewed from a particular face, anticlockwise current makes that face behave as a north pole. Clockwise current makes it behave as a south pole.
Looking from the opposite face reverses the apparent clockwise or anticlockwise direction, so specify your viewpoint.
Solenoid and Electromagnet Class 10
A solenoid is a coil containing many closely wound turns. Its field pattern resembles that of a bar magnet, with a north pole and a south pole. Inside a sufficiently long solenoid, away from its ends, the field is approximately uniform.
Parallel, nearly equally spaced field lines represent this approximately uniform region. Reversing current swaps the solenoid’s poles.
How Is an Electromagnet Made?
Placing a suitable soft-iron core inside a current-carrying coil greatly strengthens the magnetic effect. Such an electromagnet can be controlled by switching or changing the current. Soft iron is useful because it magnetises readily and retains relatively little magnetism after the current is removed.
| Arrangement | Field pattern | Useful revision point |
|---|---|---|
| Straight wire | Concentric circles around the wire. | Use the right-hand thumb rule. |
| Circular coil | Field passes through the centre along the coil’s axis. | Check current direction from a stated face. |
| Long solenoid | Bar-magnet-like pattern; approximately uniform inside. | Reversing current swaps the poles. |
| Coil with soft-iron core | A stronger field than the same coil without the core. | The arrangement acts as an electromagnet. |
Force on a Current-Carrying Conductor
A current-carrying conductor placed in a magnetic field can experience a force. For the same current, conductor length and field strength, the force is greatest when current is perpendicular to the field. It is zero when the conductor’s current direction is parallel to a uniform field.
Fleming’s Left-Hand Rule
Hold the thumb, forefinger and middle finger of your left hand mutually perpendicular:
- Forefinger: magnetic field direction.
- Middle finger: conventional current direction.
- Thumb: force or motion direction.
Worked Example: Reversing Directions
Reversing only the current reverses the force. Reversing only the magnetic field also reverses the force. Reversing both together leaves the force direction unchanged.
Choose the Correct Rule
Use the right-hand thumb rule for the magnetic field around a current-carrying straight wire. Use Fleming’s left-hand rule for the force on a current-carrying conductor in a magnetic field.
Alternating Current and Direct Current
Direct current flows in one direction. Alternating current periodically reverses direction. For sinusoidal AC, one complete cycle includes both halves of the waveform.
Example: Frequency and Time Period
For AC with frequency 50 Hz:
T = 1/f
T = 1/50
T = 0.02 s
There are 50 complete cycles each second. In sinusoidal AC, current changes direction every half-cycle, giving 100 direction reversals per second.
AC voltage can be conveniently increased or decreased using transformers. Transmitting a given power at higher voltage reduces current and helps reduce resistive energy losses in transmission wires.
Domestic Electric Circuits Class 10
Domestic appliances are connected in parallel so that each receives the supply voltage and can be operated independently. The live and neutral wires form the normal current path. An earth wire provides a protective connection for suitable appliances with exposed metal bodies.
| Component | Purpose |
|---|---|
| Live wire | Carries supply potential relative to earth. |
| Neutral wire | Provides the normal return path for current. |
| Earth wire | Provides a low-resistance fault path from an appliance’s metal body. |
| Fuse | Melts and interrupts the circuit when excessive current flows. |
| MCB | Trips to interrupt the circuit during an overcurrent condition. |
| Switch in the live wire | Disconnects the appliance from the live supply when opened. |
Overloading and Short Circuit
Overloading occurs when the current demand exceeds a circuit’s safe capacity. A short circuit creates an unintended low-resistance path, for example when live and neutral conductors contact. Both can produce excessive current and heating.
Magnetic Effects of Electric Current Class 10 MCQs
1. What is the field pattern around a straight current-carrying wire?
A. Concentric circles
B. Only straight parallel lines
C. Random intersecting lines
D. No magnetic field
Answer: A. Concentric circles. Their direction is found using the right-hand thumb rule.
2. What happens when the current in a solenoid is reversed?
A. Its poles swap
B. Its turns disappear
C. Its poles remain unchanged
D. Its field always becomes zero
Answer: A. Reversing current reverses the magnetic field direction.
3. What does the thumb represent in Fleming’s left-hand rule?
A. Magnetic field
B. Current
C. Force or motion
D. Resistance
Answer: C. Force or motion.
Assertion–Reason Practice
Assertion: The field inside a sufficiently long solenoid is approximately uniform away from its ends.
Reason: Field lines in that region are approximately parallel and equally spaced.
Answer: Both statements are true, and the reason describes the field-line representation of uniformity.
Case-Based Questions with Answers
Case Study: Compass Near a Wire
A student places a compass near a straight wire connected to a battery through a switch. Closing the switch causes the compass needle to deflect.
Question 1: Why does the needle deflect?
Current in the wire produces a magnetic field that changes
the resultant field at the compass.
Question 2: Which rule gives the wire’s field direction?
The right-hand thumb rule.
Question 3: What happens if current is reversed?
The wire’s magnetic field reverses direction.
Question 4: What happens when the switch is opened?
The wire’s current-produced field disappears, and the compass
responds to the remaining fields, including Earth’s field.
Important Questions and Diagram Practice
- State the properties of magnetic field lines.
- Draw the field around a bar magnet and mark its direction.
- Explain the field around a straight current-carrying conductor.
- Apply the right-hand thumb rule to a given current direction.
- Compare field patterns of a circular coil and a solenoid.
- Explain how a soft-iron core strengthens an electromagnet.
- Apply Fleming’s left-hand rule to determine force direction.
- Distinguish AC from DC and explain AC frequency.
- Explain parallel connections, earthing, overloading and short circuits.
How to Use This Worksheet for Revision
Attempt the worksheet without consulting notes. For direction questions, mark the current, magnetic field and viewpoint before applying a rule. For diagrams, use arrowheads and label the poles or conductor clearly.
Review errors under field patterns, direction rules, AC and DC, or domestic circuits. Repeat questions you found difficult after revising the relevant explanation.
Frequently Asked Questions
Why do magnetic field lines not intersect?
An intersection would assign two directions to the field at the same point. A non-zero magnetic field has a single direction there.
Does a stationary electric charge produce a magnetic field?
In the frame where it is stationary, it produces an electric field but no magnetic field of its own. Moving charges constitute current and produce magnetic effects.
How can the magnetic field of a coil be strengthened?
Increase current or the number of turns while keeping other relevant conditions unchanged. A suitable soft-iron core can also strengthen the field.
How can I identify the north pole of a solenoid?
Look at the current around one end. Anticlockwise current makes that face a north pole; clockwise current makes it a south pole.
When is the force on a current-carrying conductor maximum?
For fixed current, field strength and conductor length, the force is maximum when current is perpendicular to the magnetic field.
What if both current and magnetic field are reversed?
The force direction remains unchanged. Reversing either one alone reverses the force.
Does 50 Hz mean 50 direction reversals per second?
No. It means 50 complete cycles per second. Sinusoidal current reverses direction twice per cycle, giving 100 reversals per second.
Is the earth wire the normal return path for current?
No. Neutral provides the normal return path. The protective earth connection carries fault current when an appropriate fault occurs.
How is overloading different from a short circuit?
Overloading involves excessive current demand. A short circuit involves an unintended low-resistance connection. Both may cause excessive current and heating.
Where can I find related notes and a mind map?
Visit our Magnetic Effects of Electric Current notes and mind map , then return to the worksheet for practice.
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