Electric Current and Its Effects

Foundation Batch For Class 7

ELECTRIC CURRENT & ITS EFFECTS

EXPLORING ELECTRIC CURRENT

Introduction

Electric current is a flow of electric charge that powers many devices we use daily. This chapter explores how electric current works, its effects, and practical applications in circuits and devices.

1. Electric Current

What is Electric Current?

Electric current is the flow of electric charges (electrons) through a conductor.
Unit: Ampere (A).
Instrument to Measure: Ammeter.

Formula:

Current (I)=Charge (Q)/Time (t)

Where:

Q = Charge in coulombs (C).
t = Time in seconds (s).

2. Electric Circuit

Components of a Circuit

Battery/Cell: Provides energy to move charges.
Wires: Conducts electric current.
Switch: Controls the flow of current.
Load: Device that uses electric energy, like a bulb or fan.

3. Effects of Electric Current

a. Heating Effect

When electric current flows through a conductor, it produces heat.
Applications:
1. Electric iron.
2. Water heater.
3. Electric toaster.

Activity:

Connect a nichrome wire to a battery.
Observe how the wire becomes hot after some time.

b. Magnetic Effect

When electric current flows through a wire, it creates a magnetic field around it.
Applications:
1. Electromagnets.
2. Electric bells.
3. Motors.

Experiment:

Place a compass near a wire carrying current.
Observe the deflection in the compass needle due to the magnetic field.

4. Electromagnets and Their Applications

What is an Electromagnet?

A coil of wire wound around an iron core that becomes a magnet when electric current flows through it.

Uses of Electromagnets

Lifting heavy iron objects.
Electric bells.
Magnetic cranes.

How to Make an Electromagnet?

Take a long insulated wire and wrap it around an iron nail.
Connect the wire ends to a battery.
The nail behaves like a magnet when current flows.

5. Electric Bell

Working of an Electric Bell

When the switch is pressed, electric current flows through the circuit.
The electromagnet attracts the iron strip.
The hammer strikes the bell, producing sound.
The circuit breaks, and the process repeats.

Diagram:

[Illustrate a labeled diagram of an electric bell with annotations for clarity.]

6. Safety with Electricity

Precautions

Do not touch electrical appliances with wet hands.
Avoid overloading sockets.
Use proper insulation for wires.
Always switch off appliances when not in use.

7. Fun Activity

Making a Simple Circuit

Materials Needed:

Battery, wires, bulb, and a switch.

Steps:

Connect the bulb to the battery terminals using wires.
Include a switch to control the flow of current.
Observe the bulb lighting up when the circuit is complete.

Examples for Better Understanding

Heating Effect:
- Why does a filament bulb glow?
- The filament gets heated due to electric current, producing light.
Magnetic Effect:
- Why does a fan rotate?
- Electric current in the motor creates a magnetic field, causing rotation.

Practice Questions

Define electric current. What is its SI unit?
Explain the heating and magnetic effects of electric current with examples.
Draw a labeled diagram of an electric bell and explain its working.
Describe how to make an electromagnet.
What precautions should you take while using electricity?

Summary

Electric current has heating and magnetic effects that are widely used in our daily lives.
Devices like electric bells, heaters, and motors work based on these principles.
Understanding how to use electricity safely is essential for avoiding accidents.

📝 Multiple Choice Questions

1. Electric current is the flow of:
A) Atoms
B) Molecules
C) Electric charge
D) Light

2. Unit of electric current is:
A) Volt
B) Ampere
C) Ohm
D) Watt

3. Electric current is measured using:
A) Voltmeter
B) Ammeter
C) Thermometer
D) Barometer

4. Symbol of current is:
A) V
B) I
C) R
D) P

5. The formula for current is:
A) I = t/Q
B) I = Q/t
C) I = Q × t
D) I = Q + t

6. Charge is measured in:
A) Volt
B) Ampere
C) Coulomb
D) Watt

7. Time is measured in:
A) Hour
B) Minute
C) Second
D) Meter

8. A device that supplies electricity is:
A) Wire
B) Battery
C) Switch
D) Bulb

9. A complete path for current is called:
A) Circuit
B) Wire
C) Switch
D) Cell

10. A switch is used to:
A) Produce current
B) Measure current
C) Control current
D) Store current

11. Which is a conductor?
A) Plastic
B) Rubber
C) Copper
D) Wood

12. Which is an insulator?
A) Iron
B) Copper
C) Plastic
D) Silver

13. Heating effect of current produces:
A) Light only
B) Heat
C) Sound
D) Magnetism

14. Example of heating effect:
A) Fan
B) Electric iron
C) Bell
D) Motor

15. Nichrome wire is used because it:
A) Melts quickly
B) Produces heat
C) Is an insulator
D) Produces light

16. Magnetic effect of current produces:
A) Heat
B) Light
C) Magnetic field
D) Sound

17. A compass needle deflects due to:
A) Heat
B) Light
C) Magnetic field
D) Sound

18. Electromagnet is made using:
A) Plastic
B) Rubber
C) Iron core and coil
D) Glass

19. Electromagnet works when:
A) No current flows
B) Current flows
C) Battery removed
D) Wire cut

20. Which is use of electromagnet?
A) Heater
B) Bell
C) Bulb
D) Battery

21. Electric bell works on:
A) Heating effect
B) Magnetic effect
C) Light effect
D) Sound effect

22. In electric bell, hammer strikes:
A) Wire
B) Battery
C) Bell
D) Switch

23. Which device uses magnetic effect?
A) Iron
B) Heater
C) Motor
D) Bulb

24. Electric fan works using:
A) Heating effect
B) Magnetic effect
C) Light effect
D) Chemical effect

25. A bulb glows due to:
A) Magnetic effect
B) Heating effect
C) Sound effect
D) Chemical effect

26. Overloading causes:
A) Cooling
B) Heating
C) Freezing
D) Silence

27. Which is unsafe?
A) Dry hands
B) Wet hands touching switch
C) Using switch
D) Using wire

28. Insulation of wires prevents:
A) Current flow
B) Shock
C) Heat
D) Light

29. Which is NOT part of circuit?
A) Battery
B) Wire
C) Switch
D) Book

30. A closed circuit allows:
A) No current
B) Current flow
C) Light only
D) Heat only

31. An open circuit:
A) Allows current
B) Stops current
C) Increases current
D) Produces heat

32. Electric current produces:
A) Only heat
B) Only light
C) Heat and magnetic effects
D) Only sound

33. Electric current in a wire produces:
A) Sound
B) Magnetic field
C) Light
D) Water

34. Electromagnets are temporary because:
A) Always active
B) Work only with current
C) Made of plastic
D) Permanent

35. Which material is best for electromagnet core?
A) Wood
B) Plastic
C) Iron
D) Glass

36. Electric bell repeats sound due to:
A) Continuous circuit making and breaking
B) Heating
C) Cooling
D) Light

37. Safety rule:
A) Touch wires
B) Use wet hands
C) Avoid overloading
D) Break wires

38. Fuse protects by:
A) Heating
B) Breaking circuit
C) Producing light
D) Increasing current

39. Current flows through:
A) Insulators
B) Conductors
C) Air only
D) Water only

40. Which is a load?
A) Battery
B) Wire
C) Bulb
D) Switch

41. Electric heater uses:
A) Magnetic effect
B) Heating effect
C) Sound effect
D) Chemical effect

42. Which device measures current?
A) Ammeter
B) Voltmeter
C) Thermometer
D) Barometer

43. Which is correct symbol of current?
A) V
B) I
C) R
D) T

44. Which effect is used in cranes?
A) Heating
B) Magnetic
C) Light
D) Sound

45. Electric current can produce:
A) Heat
B) Magnetism
C) Light
D) All of these

46. Which device controls current?
A) Battery
B) Switch
C) Wire
D) Bulb

47. Electric circuit must be:
A) Broken
B) Open
C) Complete
D) Half

48. A conductor allows:
A) No current
B) Current flow
C) Light only
D) Heat only

49. Rubber is used as:
A) Conductor
B) Insulator
C) Magnet
D) Battery

50. Electric current is important because it:
A) Produces water
B) Powers devices
C) Stops motion
D) Breaks circuits

✅ Answer Key (At the End)

1-C, 2-B, 3-B, 4-B, 5-B, 6-C, 7-C, 8-B, 9-A, 10-C
11-C, 12-C, 13-B, 14-B, 15-B, 16-C, 17-C, 18-C, 19-B, 20-B
21-B, 22-C, 23-C, 24-B, 25-B, 26-B, 27-B, 28-B, 29-D, 30-B
31-B, 32-C, 33-B, 34-B, 35-C, 36-A, 37-C, 38-B, 39-B, 40-C
41-B, 42-A, 43-B, 44-B, 45-D, 46-B, 47-C, 48-B, 49-B, 50-B