Physics - Term 3 - Week 4

An electric circuit is a closed loop that allows current to flow. The three fundamental components of a circuit are voltage (V), current (I), and resistance (R). Voltage is the potential difference that drives the current through the circuit, current is the flow of electric charge, and resistance is the opposition to the flow of current. Ohm's Law, which states that V = I × R, is essential for understanding how these components interact.

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 the individual resistances (R_total = R1 + R2 + ... + Rn). In contrast, in a parallel circuit, components are connected across the same voltage source, and the total resistance can be calculated using the formula 1/R_total = 1/R1 + 1/R2 + ... + 1/Rn. Understanding these configurations is crucial for circuit analysis.

Consider a circuit with a voltage of 12V and a resistance of 4Ω. To find the current, we apply 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 can be calculated as R_total = R1 + R2 + R3 = 2Ω + 3Ω + 5Ω = 10Ω. This total resistance affects the current flowing through the circuit when a voltage is applied.

Let's work through a problem together. A circuit has a voltage of 24V and a resistance of 6Ω. Using Ohm's Law, calculate the current. Students should identify the formula I = V/R and substitute the values: I = 24V/6Ω = 4A. Discuss how changing the resistance would affect the current.

Now, let's calculate the total resistance for two resistors in parallel: R1 = 4Ω and R2 = 12Ω. Using the formula 1/R_total = 1/R1 + 1/R2, we find 1/R_total = 1/4 + 1/12. Students should find a common denominator and solve for R_total, which will be 3Ω. Discuss how this is less than the smallest resistor.

Students are given a worksheet with various circuit problems. For example, calculate the current in a circuit with a 30V battery and a 10Ω resistor. Another problem asks for the total resistance of three resistors in series: 5Ω, 10Ω, and 15Ω. Encourage students to show their work and apply the concepts learned.

Students will design a simple circuit using given resistors and a voltage source. They will calculate the expected current and total resistance, then simulate the circuit using a circuit simulation tool. This hands-on activity will reinforce their understanding of circuit design and analysis.

• 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 for each component
• Zero
• Dependent on the voltage only

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 becomes infinite

Answer: It decreases

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

Answer: 2A

Using Ohm's Law, I = V/R = 10V/5Ω = 2A.

• 3Ω
• 6Ω
• 9Ω
• 18Ω

Answer: 9Ω

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

• 3Ω
• 8Ω
• 16Ω
• 48Ω

Answer: 3Ω

Using the formula 1/R_total = 1/R1 + 1/R2, we find 1/R_total = 1/4 + 1/12 = 1/3, so R_total = 3Ω.