Physics - Term 4 - Week 8

An electric circuit is a closed loop that allows current to flow. It consists of various components such as resistors, capacitors, and power sources. Understanding these components is crucial for analyzing how circuits function. The flow of electric charge is driven by voltage, which is provided by sources like batteries or power supplies.

Ohm's Law is a fundamental principle in electronics that states the relationship between voltage (V), current (I), and resistance (R) in a circuit. It can be expressed with the formula V = I × R. This law allows us to calculate one of the three variables if the other two are known, making it essential for circuit analysis.

In a series circuit, components are connected end-to-end, so the same current flows through each component. The total resistance is the sum of individual resistances. In contrast, in a parallel circuit, components are connected across the same voltage source, allowing multiple paths for current. The total resistance in parallel is found using the formula 1/R_total = 1/R1 + 1/R2 + ... + 1/Rn.

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. This total resistance affects the current flowing through the circuit.

For two resistors in parallel, 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, leading to R_total = 2Ω.

Let's work through a problem together. A circuit has a voltage of 24V and a resistance of 8Ω. What is the current? Using Ohm's Law, I = V/R = 24V / 8Ω = 3A. Now, try to solve a similar problem with a voltage of 30V and a resistance of 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, calculate the total resistance if we add a third resistor of 5Ω.

In a parallel circuit with R1 = 12Ω and R2 = 4Ω, find the total resistance. Using the formula, 1/R_total = 1/12 + 1/4 = 1/12 + 3/12 = 4/12, so R_total = 3Ω. Now, try calculating the total resistance if R3 = 6Ω is added in parallel.

1. A circuit has a voltage of 15V and a resistance of 5Ω. Calculate the current. 2. Find the total resistance in a series circuit with resistors of 3Ω, 7Ω, and 2Ω. 3. Calculate the total resistance in a parallel circuit with resistors of 8Ω and 4Ω. 4. If a circuit has a current of 2A and a resistance of 10Ω, what is the voltage?

1. A circuit has three resistors in series: 5Ω, 10Ω, and 15Ω. What is the total resistance? 2. In a parallel circuit with resistors of 6Ω, 3Ω, and 2Ω, calculate the total resistance. 3. If the total current in a circuit is 5A and the total resistance is 10Ω, what is the voltage?

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

Answer: V = I × R

Ohm's Law states that voltage equals current multiplied by resistance.

• The sum of individual resistances
• The product of individual resistances
• The average of individual resistances
• None of the above

Answer: The sum of individual resistances

In a series circuit, the total resistance is simply the sum of all resistors.

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

Answer: It decreases

Adding more resistors in parallel provides additional paths for current, reducing total resistance.

Answer: 4A

Using Ohm's Law, I = V/R = 20V / 5Ω = 4A.

Answer: 15Ω

In series, total resistance is R_total = R1 + R2 = 10Ω + 5Ω = 15Ω.

• 9V
• 18V
• 3V
• 6V

Answer: 18V

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

Answer: 20Ω

Total resistance in series is R_total = R1 + R2 + R3 = 4Ω + 6Ω + 10Ω = 20Ω.

• 3Ω