Physics - Term 4 - Week 1

An electric circuit is a closed loop that allows electric current to flow. It consists of various components such as resistors, capacitors, and power sources. Understanding how these components interact is crucial for analyzing circuit behavior. The flow of current is driven by voltage, and the relationship between voltage (V), current (I), and resistance (R) is defined by Ohm's Law, which states V = I × R.

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. In contrast, parallel circuits have components 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.

Consider a circuit with a resistor of 10 ohms connected to a 5-volt battery. To find the current flowing through the circuit, we apply Ohm's Law: I = V/R. Substituting the values, we get I = 5V / 10Ω = 0.5A. This means that a current of 0.5 amperes flows through the circuit.

Suppose we have three resistors in series: R1 = 4Ω, R2 = 6Ω, and R3 = 10Ω. The total resistance (R_total) is calculated as R_total = R1 + R2 + R3 = 4Ω + 6Ω + 10Ω = 20Ω. This total resistance affects the current flowing through the circuit when connected to a voltage source.

Let's work together on a problem. A circuit has a voltage of 12 volts and a resistance of 3 ohms. Using Ohm's Law, calculate the current. Students should apply the formula I = V/R. After calculating, students will find that I = 12V / 3Ω = 4A. Discuss how changing the resistance would affect the current.

Now, let's calculate the total resistance of two resistors in parallel: R1 = 12Ω and R2 = 4Ω. We will use the formula 1/R_total = 1/R1 + 1/R2. Students will compute 1/R_total = 1/12 + 1/4, leading to R_total = 3Ω. Discuss how this lower resistance affects the overall current in the circuit.

Students will solve the following problems independently: 1) A circuit has a voltage of 24V and a resistance of 8Ω. Calculate the current. 2) Three resistors (5Ω, 10Ω, and 15Ω) are in series. Find the total resistance. 3) Two resistors (6Ω and 3Ω) are in parallel. Calculate the total resistance. Students will share their answers in pairs and discuss their methods.

• V = I × R
• R = V / I
• I = V + R
• V = R / I

Answer: V = I × R

Ohm's Law states that voltage (V) is equal to the current (I) multiplied by the resistance (R).

• It splits equally
• It is the same throughout
• It increases with each resistor
• It decreases with each resistor

Answer: It is the same throughout

In a series circuit, the same current flows through all components.

Answer: Total resistance in a parallel circuit is less than the smallest individual resistance.

In a parallel circuit, the total resistance decreases as more paths for current are added.

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

Answer: It increases

Adding resistors in series increases the total resistance because the current has to pass through each resistor sequentially.

Answer: 2A

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

• 3Ω
• 4Ω
• 12Ω
• 16Ω

Answer: 3Ω

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

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

Answer: It doubles

According to Ohm's Law, if voltage increases and resistance remains constant, current will also increase.