Physics - Term 4 - Week 8

Electric circuits consist of a source of voltage, conductors, and a load. Voltage (V) is the potential difference that drives current (I) through the circuit. Resistance (R) opposes the flow of current and is measured in ohms (Ω). Ohm's Law states that V = I × R, which allows us to calculate any one of these three quantities if the other two are known.

In a series circuit, components are connected end-to-end, so the same current flows through each component. The total resistance (R_total) in a series circuit is the sum of the individual resistances: R_total = R1 + R2 + R3 + ... In contrast, in a parallel circuit, components are connected across the same voltage source, and the total current is the sum of the currents through each branch. The total resistance in a parallel circuit can be calculated using the formula: 1/R_total = 1/R1 + 1/R2 + 1/R3 + ... .

Consider a circuit with a voltage of 12V and a resistance of 4Ω. To find the current, we use Ohm's Law: I = V/R = 12V/4Ω = 3A. This means that a current of 3 amperes flows through the circuit.

If we have three resistors in series: R1 = 2Ω, R2 = 3Ω, and R3 = 5Ω, the total resistance is R_total = R1 + R2 + R3 = 2Ω + 3Ω + 5Ω = 10Ω. Therefore, the total resistance of the series circuit is 10 ohms.

Given a circuit with a voltage of 24V and a resistance of 6Ω, calculate the current. Students should apply Ohm's Law: I = V/R. The expected answer is I = 24V/6Ω = 4A.

Consider two resistors in parallel: R1 = 4Ω and R2 = 12Ω. Students should use the parallel resistance formula: 1/R_total = 1/R1 + 1/R2. The calculation leads to 1/R_total = 1/4 + 1/12, which simplifies to R_total = 3Ω.

Students are tasked with calculating the current in a circuit with a voltage of 30V and a resistance of 10Ω. They should show their work and arrive at the answer: I = 30V/10Ω = 3A.

Students will calculate the total resistance of a circuit with three resistors in series: R1 = 5Ω, R2 = 10Ω, and R3 = 15Ω. They should find R_total = R1 + R2 + R3 = 5Ω + 10Ω + 15Ω = 30Ω.

• Volts
• Amperes
• Ohms
• Watts

Answer: Ohms

Resistance is measured in ohms (Ω), which quantifies how much a material opposes the flow of electric current.

• The same through all components
• Different in each component
• Zero
• Dependent on the voltage

Answer: The same through all components

In a series circuit, the same current flows through each component because there is only one path for the current to take.

Answer: V = I × R

Ohm's Law relates voltage (V), current (I), and resistance (R) in an electrical circuit.

• It increases
• It decreases
• It remains the same
• It doubles

Answer: It decreases

Adding more resistors in parallel provides additional paths for current, which decreases the total resistance.

Answer: 5A

Using Ohm's Law, I = V/R = 50V/10Ω = 5A.

• 9Ω
• 18Ω
• 2Ω
• 3Ω

Answer: 9Ω

In a series circuit, total resistance is the sum: R_total = R1 + R2 = 6Ω + 3Ω = 9Ω.

Answer: 2Ω

Using the formula for parallel resistors: 1/R_total = 1/R1 + 1/R2 = 1/4 + 1/4 = 1/2, thus R_total = 2Ω.