Physics - Term 4 - Week 6

An electric circuit is a closed loop that allows current to flow from a power source, through various components, and back to the source. The basic components of a circuit include a power source (like a battery), conductors (wires), and loads (like resistors or light bulbs). Understanding how these components interact is crucial for analyzing circuit behavior.

Ohm's Law states that the current (I) flowing through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R) of the conductor. This relationship can be expressed with the formula V = I × R. This law is fundamental in calculating the behavior of circuits.

In a series circuit, components are connected end-to-end, so the same current flows through all components. The total resistance in a series circuit is the sum of the individual resistances. 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 essential for circuit design.

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

Consider a series circuit with three resistors: R1 = 2Ω, R2 = 3Ω, and R3 = 5Ω. The total resistance (R_total) is calculated as R_total = R1 + R2 + R3 = 2Ω + 3Ω + 5Ω = 10Ω. Therefore, the total resistance in this series circuit is 10 ohms.

For a parallel circuit with two resistors, R1 = 6Ω and R2 = 3Ω, we calculate the total resistance using the formula 1/R_total = 1/R1 + 1/R2. Thus, 1/R_total = 1/6 + 1/3 = 1/6 + 2/6 = 3/6. Therefore, R_total = 6/3 = 2Ω. The total resistance in this parallel circuit is 2 ohms.

Let's work through a problem together. If we have a circuit with a voltage of 24V and a resistance of 8Ω, what is the current? Using Ohm's Law, I = V/R, we find I = 24V / 8Ω = 3A. Now, try to solve a similar problem: What is the current if the voltage is 30V and the resistance is 10Ω?

Consider a series circuit with two resistors: R1 = 4Ω and R2 = 6Ω. What is the total resistance? R_total = R1 + R2 = 4Ω + 6Ω = 10Ω. Now, let's add a third resistor, R3 = 2Ω. What is the new total resistance?

In a parallel circuit with two resistors, R1 = 12Ω and R2 = 4Ω, calculate the total resistance. Using the formula 1/R_total = 1/R1 + 1/R2, we find 1/R_total = 1/12 + 1/4 = 1/12 + 3/12 = 4/12. Therefore, R_total = 12/4 = 3Ω. Now, try calculating the total resistance if R1 = 8Ω and R2 = 2Ω.

1. A circuit has a voltage of 15V and a resistance of 5Ω. Calculate the current. 2. In a series circuit with resistors of 3Ω, 5Ω, and 7Ω, find the total resistance. 3. For a parallel circuit with resistors of 10Ω and 5Ω, calculate the total resistance. 4. If a circuit has a voltage of 20V and a current of 4A, what is the resistance?

1. Calculate the current in a circuit with a voltage of 50V and a resistance of 10Ω. 2. In a series circuit with three resistors of 2Ω, 3Ω, and 4Ω, what is the total resistance? 3. For a parallel circuit with resistors of 6Ω, 3Ω, and 2Ω, find the total resistance. 4. If the total resistance in a circuit is 12Ω and the current is 2A, what is the voltage?

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

Answer: V = I × R

Ohm's Law states that voltage is equal to the current multiplied by resistance.

• R_total = R1 + R2 + R3
• R_total = 1/R1 + 1/R2
• R_total = R1 × R2
• R_total = R1 - R2

Answer: R_total = R1 + R2 + R3

In a series circuit, the total resistance is the sum of all individual resistances.

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

Answer: It decreases

Adding more resistors in parallel decreases the total resistance.

Answer: 2A

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

Answer: 10Ω

In a series circuit, R_total = R1 + R2 = 4Ω + 6Ω = 10Ω.

• 2Ω
• 4Ω
• 8Ω
• 16Ω

Answer: 2Ω

Using the formula 1/R_total = 1/R1 + 1/R2, we find R_total = 2Ω.

• 9V
• 18V
• 3V
• 6V

Answer: 18V

Using Ohm's Law, V = I × R = 3A × 6Ω = 18V.