QCM : Electricity Magnetic and Heating Effects — 22 questions

Explication

When current stops, the magnetic effect of the current-carrying wire disappears, so the compass returns to its original direction. The other options incorrectly suggest a persistent magnetism or a heating cause.

Explication

The magnetic effect of electric current is the magnetic field produced around a conductor when current flows. It is not primarily the heating effect described for resistance.

Explication

A magnetic field is the region around a magnet or current-carrying wire where its magnetic effect can be felt. It is not the current itself that is the region.

Explication

Compass deflection shows that the magnetic field produced by the current is acting on the compass needle. Heat from the wire is not the explanation given for the deflection.

Explication

A current-carrying coil that behaves as a magnet is called an electromagnet. A permanent magnet does not require current to act.

Explication

An iron nail in the coil core makes the coil a stronger magnet, increasing compass deflection. The coil still needs current; the effect is not current-free.

Explication

When current flows the electromagnet attracts, and when current stops it loses the magnetic effect, so its magnetism is temporary. Permanent magnetism would not switch off like this.

Explication

Strength increases by increasing the current and/or the number of turns of the coil. Changing only direction reverses poles rather than increasing strength.

Explication

The poles are reversed by changing the direction of the current through the coil. Other changes can affect strength but do not specifically describe reversing poles.

Explication

Warming of a conductor due to current is called the heating effect of electric current. Magnetic effects relate to compass deflection, not heating.

Explication

Current encounters resistance, and that resistance turns some electrical energy into heat. The other options do not match the resistance-to-heat mechanism.

Explication

Nichrome offers higher resistance than a copper wire of the same size and length. The distractors incorrectly claim copper matches nichrome or that resistance depends only on battery cells.

Explication

Electric room heaters and kettles work mainly by the heating effect of electric current. Fans, for example, are a common distractor because they rely on motors rather than mainly on heating.

Explication

The rod or coil of wire inside the appliance that gets heated is the heating element. The outer body is a plausible distractor because it may feel warm but is not the part meant to generate heat.

Explication

Heating effect can lead to energy loss and overheating of plugs and sockets, potentially melting plastic and causing fires. The distractors incorrectly claim safety or energy conversion without heat.

Explication

A Voltaic cell has two metal rods of different materials partly dipped in an electrolyte in a container. A dry cell is a common distractor, but it does not use a liquid electrolyte.

Explication

The liquid in a Voltaic cell is the electrolyte. A common confusion is to swap it with the metal electrodes dipped into it.

Explication

Electricity is produced when chemical reactions occur between the electrodes and the electrolyte. The distractors reflect the misconception that electricity is merely stored in the metals.

Explication

A dry cell uses a thick moist paste instead of a liquid electrolyte. Students may mix it up with a Voltaic cell because both generate electricity chemically.

Explication

In a dry cell, the zinc container acts as the negative terminal. A plausible distractor is the carbon rod, which actually serves as the positive terminal.

Explication

Rechargeable batteries can be recharged and reused multiple times. A common distractor is an ordinary dry cell, which is generally single-use.

Explication

Used batteries should go to e-waste recycling because they can contain harmful substances and also valuable recyclable materials. A distractor reflects the misconception that a dead battery is harmless waste.