Understanding Ohm's Law and Circuits

What is Ohm's Law?

• It states that the current through a conductor between two points is directly proportional to the voltage across the two points.

• It states that the resistance in a circuit is inversely proportional to the current.

• It states that the power in a circuit is directly proportional to the resistance.

• It states that the voltage in a circuit is inversely proportional to the power.

Answer explanation

Ohm's Law states that the current through a conductor is directly proportional to the voltage across it, which is accurately described in the correct answer choice. The other options misinterpret the relationships in electrical circuits.

What is the formula for Ohm's Law?

Answer explanation

Ohm's Law states that voltage (V) is equal to the current (I) multiplied by the resistance (R). Therefore, the correct formula is V = I × R, which is the first answer choice.

Which of the following is an application of Ohm's Law?

• Calculating the speed of light in a vacuum.

• Determining the resistance needed for a specific current in an electrical circuit.

• Measuring the gravitational force between two masses.

• Estimating the energy consumption of a chemical reaction.

Answer explanation

Ohm's Law relates voltage, current, and resistance in an electrical circuit. Thus, determining the resistance needed for a specific current directly applies Ohm's Law, making it the correct choice.

In a series circuit, how does the total resistance compare to the individual resistances?

• The total resistance is the sum of the individual resistances.

• The total resistance is the product of the individual resistances.

• The total resistance is the average of the individual resistances.

• The total resistance is the difference between the largest and smallest resistances.

Answer explanation

In a series circuit, the total resistance is calculated by adding all individual resistances together. This means the correct choice is that the total resistance is the sum of the individual resistances.

In a parallel circuit, how is the total resistance calculated?

• The total resistance is the sum of the individual resistances.

• The total resistance is the reciprocal of the sum of the reciprocals of the individual resistances.

• The total resistance is the product of the individual resistances.

• The total resistance is the average of the individual resistances.

Answer explanation

In a parallel circuit, the total resistance is calculated using the formula: 1/R_total = 1/R1 + 1/R2 + ... + 1/Rn. This means the total resistance is the reciprocal of the sum of the reciprocals of the individual resistances.

Which factor does NOT affect the resistance of a conductor?

• Length of the conductor

• Cross-sectional area of the conductor

• Material of the conductor

• Colour of the conductor

Answer explanation

The resistance of a conductor is affected by its length, cross-sectional area, and material. However, the colour of the conductor does not influence its resistance, making it the correct choice.

What happens to the resistance of a wire if its length is doubled?

• The resistance is halved.

• The resistance remains the same.

• The resistance is doubled.

• The resistance is quadrupled.

Answer explanation

The resistance of a wire is directly proportional to its length. If the length is doubled, the resistance also doubles, making the correct answer "The resistance is doubled."

How does temperature generally affect the resistance of a metallic conductor?

• Resistance decreases as temperature increases.

• Resistance increases as temperature increases.

• Resistance remains constant regardless of temperature.

• Resistance fluctuates randomly with temperature changes.

Answer explanation

In metallic conductors, as temperature increases, the atoms vibrate more, causing more collisions with electrons. This results in increased resistance, making the correct choice "Resistance increases as temperature increases."

What is the unit of resistance?

• Ampere

• Volt

• Ohm

• Watt

Answer explanation

The unit of resistance is the Ohm, which measures how much a material opposes the flow of electric current. Ampere measures current, Volt measures voltage, and Watt measures power, making Ohm the correct choice.

If a circuit has a voltage of 12 volts and a resistance of 4 ohms, what is the current flowing through the circuit?

• 2 amperes

• 3 amperes

• 4 amperes

• 6 amperes

Answer explanation

To find the current, use Ohm's Law: I = V/R. Here, V = 12 volts and R = 4 ohms. So, I = 12/4 = 3 amperes. Therefore, the correct answer is 3 amperes.