Physics - Term 3 - Week 2

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) is the opposition to the flow of current, measured in ohms (Ω). Ohm's Law states that V = I × R, which allows us to calculate any one of these 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 in a series circuit is the sum of individual resistances (R_total = R1 + R2 + ... + Rn). In contrast, in a parallel circuit, components are connected across the same voltage source, allowing multiple paths for current. The total resistance in a parallel circuit can be calculated using the formula 1/R_total = 1/R1 + 1/R2 + ... + 1/Rn.

If a circuit has a voltage of 12 volts and a resistance of 4 ohms, we can find the current using Ohm's Law. I = V/R = 12V / 4Ω = 3A. Therefore, the current flowing through the circuit is 3 amperes.

Consider a series circuit with three resistors: R1 = 2Ω, R2 = 3Ω, and R3 = 5Ω. The total resistance is R_total = R1 + R2 + R3 = 2Ω + 3Ω + 5Ω = 10Ω. This means the total resistance that the current must overcome is 10 ohms.

Using the circuit with a 9V battery and a 3Ω resistor, calculate the current flowing through the circuit. Apply Ohm's Law: I = V/R = 9V / 3Ω = 3A. Discuss with your peers how changing the resistance would affect the current.

In a parallel circuit with two resistors, R1 = 6Ω and R2 = 3Ω, calculate the total resistance. Use the formula: 1/R_total = 1/R1 + 1/R2. Therefore, 1/R_total = 1/6 + 1/3 = 1/6 + 2/6 = 3/6, so R_total = 2Ω. Work in pairs to explore how adding more resistors in parallel affects the total resistance.

Solve the following problems independently: 1) A circuit has a voltage of 24V and a resistance of 8Ω. What is the current? 2) Calculate the total resistance of a series circuit with resistors of 4Ω, 5Ω, and 6Ω. 3) In a parallel circuit with resistors of 12Ω and 4Ω, what is the total resistance? Show your work and be prepared to discuss your solutions.

• Volts
• Amperes
• Ohms
• Watts

Answer: Ohms

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

• It doubles
• It halves
• It remains the same
• It quadruples

Answer: It doubles

According to Ohm's Law, if voltage increases while resistance stays the same, current will also increase proportionally.

Answer: V = I × R

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

• 15Ω
• 5Ω
• 10Ω
• 50Ω

Answer: 15Ω

In a series circuit, total resistance is the sum of individual resistances: R_total = R1 + R2 = 5Ω + 10Ω = 15Ω.

• It increases
• It decreases
• It remains the same
• It becomes zero

Answer: It increases

In a parallel circuit, if one resistor fails, the total resistance increases because there are fewer paths for current to flow.

Answer: 3A

Using Ohm's Law: I = V/R = 12V / 4Ω = 3A.

• 2Ω
• 4Ω
• 8Ω
• 16Ω

Answer: 2Ω

Using the parallel resistance formula: 1/R_total = 1/R1 + 1/R2 = 1/4 + 1/4 = 1/2, so R_total = 2Ω.