Physics - Term 3 - Week 9

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. The flow of current is driven by voltage, which is the potential difference between two points in the circuit. Understanding how these components interact is crucial for analyzing and designing circuits.

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 each component. 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.

If a circuit has a voltage of 12 volts and a resistance of 4 ohms, we can find the current using Ohm's Law. Rearranging the formula gives us I = V/R. Substituting the values, we get I = 12V / 4Ω = 3A. Thus, 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 (R_total) is calculated as R_total = R1 + R2 + R3 = 2Ω + 3Ω + 5Ω = 10Ω. Therefore, the total resistance in the 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. This gives us 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. A circuit has a voltage of 24 volts and a resistance of 8 ohms. What is the current? Using Ohm's Law, we can find the current: I = V/R = 24V / 8Ω = 3A. Now, try calculating the current for a circuit with a voltage of 30 volts and a resistance of 10 ohms.

In a series circuit with two resistors, R1 = 4Ω and R2 = 6Ω, calculate 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?

Consider a parallel circuit with three resistors: R1 = 12Ω, R2 = 4Ω, and R3 = 3Ω. Calculate the total resistance. Start by finding 1/R_total = 1/R1 + 1/R2 + 1/R3 = 1/12 + 1/4 + 1/3. Simplifying this will give you the total resistance.

1. A circuit has a voltage of 15 volts and a resistance of 5 ohms. 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 current of 2A and a resistance of 4Ω, what is the voltage?

1. A circuit has a total resistance of 12Ω and a current of 2A. What is the voltage? 2. Calculate the total resistance of a parallel circuit with resistors of 8Ω, 4Ω, and 2Ω. 3. If the voltage across a resistor is 20V and the current is 5A, what is the resistance?

• 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).

• 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 calculated by adding all individual resistances together.

• It increases
• It decreases
• It stays the same
• It doubles

Answer: It decreases

Adding more resistors in parallel decreases the total resistance because the current has multiple paths to flow.

Answer: 2A

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

Answer: 10Ω

The total resistance is R_total = R1 + R2 + R3 = 2Ω + 3Ω + 5Ω = 10Ω.

Answer: 18V

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

• They share the same current
• They share the same voltage
• They have the same resistance
• They cannot be combined

Answer: They share the same voltage

In a parallel circuit, all components share the same voltage across them.