"Electricity: Magnetic and Heating Effects" — Practice

Question 1

A coil of copper wire is wound on a rolled paper cylinder with nothing inside it and connected to a cell. A compass is placed near one end. What happens?

Accepted Answer

The needle deflects, because the current produces a magnetic field

Question 2

Which statement about a dry cell is correct?

Accepted Answer

The zinc container is the negative terminal and the carbon rod the positive

Question 3

An electromagnet is connected to a cell and lifts 5 paper clips. Which change would leave the strength unchanged but swap its north and south ends?

Accepted Answer

Reversing the connections at the cell

Question 4

Assertion (A): Nichrome, not copper, is used for the heating element of an electric iron. Reason (R): Nichrome offers a higher resistance than copper of the same size and length.

Accepted Answer

Both A and R are true, and R is the correct explanation of A

Question 5

An iron nail and a copper strip are dipped into a beaker of pure water and connected through an LED and a switch. The switch is closed. What happens?

Accepted Answer

The LED does not glow, because pure water is not an electrolyte

Question 6

Why does the chapter test the cylindrical coil with only a paper cylinder inside it BEFORE inserting the iron nail? What would be lost if the wire had simply been wound straight onto the nail?

Accepted Answer

So that the coil's own effect can be separated from the iron core's contribution.

Question 7

A student writes: 'The wire in Sumana's electromagnet was still warm, so current must still have been flowing, so the cell cannot be the problem.' Where does this reasoning go wrong?

Accepted Answer

It treats 'some current' and 'enough current' as the same thing.

Question 8

The chapter says an electromagnet's poles can be reversed by reversing the current. Explain why this makes an electromagnet more useful than a permanent magnet, and name one thing about an electromagnet that a permanent magnet does better.

Accepted Answer

Switchability and adjustability, against the permanent magnet's independence from a power supply.

Practice — "Electricity: Magnetic and Heating Effects"

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