Physics Electric Current & Circuits Part 14 (Question 2) Class 7 VII

TL;DR

Electric current flowing through a wire generates a magnetic field, causing a nearby compass needle to be deflected. The deflection disappears when there is no current flow or the circuit is open.

Transcript

hello friends this video on electric current and its effects part 14 is brought to you by example.com no more fear from exam question number six when the current is switched on through a wire a compass needle kept nearby gets deflected from its north south position explain now this is all about the magnetic effect of current so you have current pas... Read More

Key Insights

• 🧭 A current passing through a wire generates a magnetic field, causing a compass needle nearby to deflect.
• 😚 A circuit must be closed and have a source of current (such as a cell) for a magnetic field to be produced.
• 🫥 The longer line in the symbol for a cell represents its positive terminal, and multiple cells combined form a battery.
• 🎭 When current flows through a room heater, it produces heat to provide warmth.
• 😕 A fuse is a safety device that prevents damage to electrical devices by stopping excessive current flow.
• 🫑 Electromagnets attract pieces of iron and are used in devices like electric bells.
• 🫠 Normal wires used in electrical circuits have high melting points and cannot substitute for fuses.

Questions & Answers

Q: Why does the compass needle deflect when current is switched on through a wire?

The deflection occurs because the current flowing through the wire creates a magnetic field, and the compass needle, being a tiny magnet itself, is attracted to the magnetic field, causing it to deflect.

Q: Will the compass needle show deflection when the switch in the circuit is closed?

No, when the circuit is closed but there is no cell in the circuit to generate current, there will be no current flow, no magnetic field produced, and therefore no deflection in the compass needle.

Q: What is the purpose of a fuse in an electrical circuit?

A fuse is a safety device that prevents damage to electrical devices from excessive flow of current. It has a wire filament with a low melting point, which melts and breaks the circuit when the current exceeds a certain limit.

Q: Can an electromagnet be used to separate plastic bags from a garbage heap?

No, an electromagnet can only attract magnetic materials like iron. Since plastic is not magnetic, an electromagnet would not be useful for separating plastic bags from a garbage heap.

Summary & Key Takeaways

• When a current passes through a wire, a magnetic field is created, causing a nearby compass needle to deflect due to the attraction between the magnetic field and the needle.

• If the current is not flowing or the circuit is open, there will be no magnetic field and therefore no deflection in the compass needle.

• The longer line in the symbol for a cell represents its positive terminal, and a battery is formed by combining multiple cells. When the current is switched on in a room heater, heat is produced.

• A fuse is a safety device that prevents excessive current flow and protects electrical devices from damage. Electromagnets attract pieces of iron, and an electric bell contains an electromagnet.