Electric Current and Its Effects — Class 7 Science NCERT Solutions (Free)

Free step-by-step NCERT solutions for Class 7 Science chapter "Electric Current and Its Effects" — 8 important questions with detailed answers for CBSE board exam preparation.

TL;DR: Free step-by-step NCERT solutions for Class 7 Science chapter "Electric Current and Its Effects" — 8 important questions with detailed answers for CBS…

By Syllab.in · Updated Jun 14, 2026

Key Questions Covered:

Define electric current. What is its SI unit?
What are the effects of electric current? Give examples.
Explain the magnetic effect of electric current.
What is an electromagnet? How is it made?
How does an electric bell work?
What is the heating effect of electric current? Why does a fuse melt?
+ 2 more questions in the full chapter

Solutions Summary:

Question	Status
Define electric current. What is its SI unit?	✓ Solved
What are the effects of electric current? Give examples.	✓ Solved
Explain the magnetic effect of electric current.	✓ Solved
What is an electromagnet? How is it made?	✓ Solved
How does an electric bell work?	✓ Solved
What is the heating effect of electric current? Why does …	✓ Solved

Showing 6 of 8 questions

Q1: Define electric current. What is its SI unit?

Electric current: flow of electric charge through a conductor. It is the amount of charge flowing per unit time. Represented by symbol I. SI unit: Ampere (A), named after scientist André-Marie Ampère. 1 A = 1 Coulomb / 1 second (C/s). Device: Ammeter measures current (connected in series in circuit).

Q2: What are the effects of electric current? Give examples.

Effects of electric current: 1. Heating effect: resistive heating in wires (electric heater, light bulb filament, fuse melts when current exceeds limit) 2. Magnetic effect: current carrying conductor creates magnetic field (electromagnet, electric bell, relay) 3. Chemical effect: chemical changes when current passes through solution (electroplating, electrolysis) 4. Lighting effect: current in gases produces light (neon tubes, discharge lamps)

Q3: Explain the magnetic effect of electric current.

When electric current flows through a conductor, it generates a magnetic field around the conductor. Direction of magnetic field follows right-hand rule: thumb points in direction of current, fingers curl in direction of field. Applications: Electromagnet (solenoid with iron core produces strong magnet), Electric bell (electromagnet pulls armature), Relay (electromagnet controls switching), Motor (current in magnetic field produces force).

Q4: What is an electromagnet? How is it made?

Electromagnet: temporary magnet created by passing electric current through a coil of insulated wire wound around an iron core. How it works: current through coil creates magnetic field that magnetizes iron core. Construction: Insulated copper wire wound in coil, iron rod inside coil, ends connected to power source. Advantage: Strength can be controlled by varying current; magnetism disappears when current is switched off.

Q5: How does an electric bell work?

Working of electric bell: Step 1: Current flows through electromagnet. Step 2: Electromagnet attracts iron armature (attached to hammer). Step 3: Hammer strikes the bell, producing sound. Step 4: As armature moves, it breaks contact with screw, circuit opens. Step 5: Electromagnet loses magnetism, spring pulls armature back. Step 6: Contact is re-established, current flows again. Step 7: Process repeats rapidly, producing continuous ringing.

Q6: What is the heating effect of electric current? Why does a fuse melt?

Heating effect: When electric current flows through a conductor, it generates heat due to resistance. Heat produced = I²Rt (Joule's law), where I = current, R = resistance, t = time. Fuse: Thin wire of alloy (low melting point) in series with circuit. When current exceeds safe limit, excessive heat is produced, fuse wire melts, breaks circuit, prevents damage to appliances and fire hazard. Different appliances have different rated fuses.

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