Chemical and Magnetic Effects of Electric Current Quiz

A student connects a battery to a straight wire and places a compass around it. The compass needle deflects. What will happen if the battery terminals are reversed?

1. The compass needle deflects in the opposite direction.
2. The compass needle stops moving completely.
3. The magnetic field around the wire disappears.
4. The compass needle starts rotating continuously.

Answer: (a) The compass needle deflects in the opposite direction.

A student observes that a magnetic compass needle deflects when placed near a straight current-carrying wire. What does this indicate?

1. The wire has become a permanent magnet.
2. The wire is repelling the Earth’s magnetic field.
3. The current in the wire creates a magnetic field.
4. The compass needle is malfunctioning.

Answer: (c) The current in the wire creates a magnetic field.

A student builds an electromagnet by wrapping a wire around an iron nail and connecting it to a battery. However, the magnet is too weak. What could be a possible reason?

1. The wire is wound too many times around the nail.
2. The nail is made of aluminium instead of iron.
3. The battery is too powerful.
4. The wire is made of plastic instead of copper.

Answer: (d) The wire is made of plastic instead of copper.

A student wants to test whether a given liquid is an electrolyte. Which setup will best help them determine this?

1. Using a voltmeter to check for voltage across the liquid
2. Placing a thermometer in the liquid to see if temperature changes
3. Connecting the liquid between two metal electrodes and observing if a bulb glows
4. Measuring the mass of the liquid before and after the test

Answer: (c) Connecting the liquid between two metal electrodes and observing if a bulb glows

During electrolysis of copper sulphate (CuSO₄) solution using copper electrodes, the mass of the anode decreases over time. What is the best explanation for this observation?

1. The anode dissolves in water due to oxidation.
2. The anode loses copper ions, which migrate to the cathode.
3. The anode undergoes reduction, losing electrons.
4. Copper sulphate breaks down completely into copper and sulphate ions.

Answer: (b) The anode loses copper ions, which migrate to the cathode.

A diagram shows electrolysis of acidified water using platinum electrodes. The volume of gas collected at the cathode is twice the volume collected at the anode. What is the correct reason for this observation?

1. Oxygen is heavier, so it forms in a smaller volume than hydrogen.
2. Hydrogen gas dissolves more easily in water than oxygen gas.
3. Platinum electrodes favour hydrogen gas formation over oxygen gas.
4. Water contains twice as many hydrogen atoms as oxygen atoms.

Answer: (d) Water contains twice as many hydrogen atoms as oxygen atoms.

A student tests whether a solid salt crystal conducts electricity by placing electrodes on it. The bulb does not glow. The student then dissolves the salt in water, and the bulb glows brightly. What does this indicate?

1. Ionic compounds only conduct when dissolved or molten, not in solid form.
2. Solid salt blocks electricity by trapping electrons inside.
3. Salt gains extra electrons in water, making it conductive.
4. Water chemically reacts with salt to generate electricity.

Answer: (a) Ionic compounds only conduct when dissolved or molten, not in solid form.

A student is testing the conductivity of four different liquids using a simple circuit with a bulb. The bulb glows brightly in saltwater but dimly in lemon juice. What is the most likely reason for this difference?

1. Saltwater has a higher concentration of free ions than lemon juice.
2. Lemon juice contains no charged particles for conduction.
3. The acidity of lemon juice prevents electricity from flowing.
4. The salt in saltwater chemically reacts with the electrodes to create more current.

Answer: (a) Saltwater has a higher concentration of free ions than lemon juice.

A student places several compass needles around a vertical current-carrying wire. The diagram shows that the compass needles align in circular patterns. If the wire is flipped upside down while keeping the same current direction, what will happen to the compass needles?

1. The compass needles will point in the same direction as before.
2. The compass needles will point in the opposite direction.
3. The compass needles will move closer to the wire due to attraction.
4. The compass needles will become randomly oriented.

Answer: (b) The compass needles will point in the opposite direction.

A student investigates how wire shape affects the magnetic field. The diagram shows a straight wire with circular magnetic field lines and a circular loop with a different pattern of field lines. What will happen if multiple loops are stacked together to form a coil?

1. The magnetic field will remain the same as a single loop.
2. The magnetic field will cancel out completely.
3. The magnetic field will become stronger and resemble a bar magnet’s field.
4. The direction of the field will reverse at the centre of the coil.

Answer: (c) The magnetic field will become stronger and resemble a bar magnet’s field.