Y08 Electricity Review

A circuit has a potential difference of 24 V and a total resistance of 8 Ω. What is the current flowing through the circuit?

• 2 A

• 3 A

• 4 A

• 5 A

Answer explanation

To find the current, use Ohm's Law: I = V/R. Here, V = 24 V and R = 8 Ω. So, I = 24 V / 8 Ω = 3 A.

If a circuit has a resistance of 15 Ω and a current of 2 A, what is the potential difference across the circuit?

• 20 V

• 25 V

• 30 V

• 35 V

Answer explanation

Using Ohm's Law (V = I × R), where V is potential difference, I is current, and R is resistance: V = 2 A × 15 Ω = 30 V. Therefore, the potential difference across the circuit is 30 V.

Which statement describes the current in a series circuit?

• The current varies at different points in the circuit.

• The current is the same throughout the circuit.

• The current decreases as it passes through each component.

• The current increases at each component.

Answer explanation

In a series circuit, the current remains constant throughout all components. This means that the same amount of current flows through each part of the circuit, making 'The current is the same throughout the circuit' the correct statement.

Which statement describes the voltage in a series circuit?

• The voltage is the same across each component.

• The total voltage is the sum of the voltages across each component.

• The voltage increases at each component.

• The voltage decreases uniformly across the circuit.

Answer explanation

In a series circuit, the total voltage supplied by the source is divided among the components. Therefore, the correct statement is that the total voltage is the sum of the voltages across each component.

If the length of a wire is doubled, what happens to its resistance?

• The resistance is halved.

• The resistance stays the same.

• The resistance doubles.

• The resistance quadruples.

Answer explanation

When the length of a wire is doubled, its resistance also doubles. This is due to the direct relationship between resistance and length, as described by the formula R = ρ(L/A), where R is resistance, ρ is resistivity, L is length, and A is cross-sectional area.

If the thickness of a wire is increased, what happens to its resistance?

• The resistance decreases.

• The resistance stays the same.

• The resistance increases.

Answer explanation

When the thickness of a wire increases, its cross-sectional area also increases. According to the formula for resistance (R = ρL/A), where A is the area, an increase in A leads to a decrease in resistance. Thus, the resistance decreases.

What happens when you rub two materials together?

• They become colder.

• They create friction.

• They glow in the dark.

Answer explanation

When you rub two materials together, they create friction due to the resistance between their surfaces. This friction can generate heat, but it does not make them colder or cause them to glow in the dark.

What happens when opposite magnetic poles are near each other?

• They repel

• They attract

• They have no effect

Answer explanation

When opposite magnetic poles are near each other, they attract each other due to the fundamental property of magnets. This attraction occurs because opposite poles create a magnetic field that pulls them together.

Why does your hair stand on end when you touch a Van de Graaff generator?

• The hair becomes wet

• Each strand gains the same electric charge and repels each other

• The generator creates a magnetic field

Answer explanation

When you touch a Van de Graaff generator, it transfers electric charge to your hair. Each strand gains the same charge, causing them to repel each other, which makes your hair stand on end.

What are the main components of an atom's nucleus?

• Electrons and protons

• Protons and neutrons

• Electrons and neutrons

• Neutrons

Answer explanation

The nucleus of an atom is primarily composed of protons and neutrons. Protons carry a positive charge, while neutrons are neutral. Electrons, which are negatively charged, orbit the nucleus but are not part of it.