Science · Class 7
Electric Current and Its Effects
Heating effect, magnetic effect of current, and electromagnets.
4 sections15–25 min read6 MCQs · 2 examples
Chapter Overview
Electric current is flow of charge. This chapter covers circuit components, heating effect (fuse, heater), magnetic effect (electromagnet, electric bell), and chemical effect (electroplating).
Electric Current
- Cell provides potential difference; current flows in closed circuit
- Ammeter in series; voltmeter in parallel
- 1 A = 1 C/s; conventional current: + to − outside cell
Heating Effect
- H = I²Rt (Joule heating); used in heater, iron, fuse
- Fuse: melts when current exceeds safe limit
- Nichrome wire high resistance — glows hot
Magnetic Effect
- Current-carrying wire has magnetic field
- Electromagnet: coil around iron core
- Electric bell: electromagnet attracts hammer
- Motor uses magnetic effect
Solved Examples
Step-by-step solutions — read each step before checking the final answer.
Fuse
Why is fuse wire thin and made of alloy?
- 1High resistance, low melting point
- 2Melts when current too high
- 3Protects appliances and wiring
Answer
Safety device — breaks circuit on overload
Electromagnet
How is electromagnet made stronger?
- 1More turns in coil
- 2More current
- 3Iron core inside coil
Answer
Increase turns, current, or use soft iron core
Key Points to Remember
- ✓ LED uses less power than bulb
- ✓ MCB replaces fuse in modern homes
- ✓ Electroplating coats metal with another metal
Exam Tips
- • Draw circuit with ammeter and voltmeter correctly
- • Explain working of electric bell
- • List applications of heating effect
Practice MCQs — Electric Current and Its Effects
Test your understanding with topic-wise multiple choice questions. Explanations appear after each answer.
Question 1 of 6Score: 0/0
Heating effect depends on: