Physics - Term 4 - Week 7

An electric circuit is a closed loop that allows electric current to flow. The basic components of a circuit include a power source (like a battery), conductors (wires), and loads (like resistors or 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 electrical 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 common points, and the voltage across each component is the same. 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 voltage of 12 volts and a resistance of 4 ohms. To find the current, we use Ohm's Law: I = V/R. Substituting the values, we get I = 12V / 4Ω = 3A. Thus, the current flowing through the circuit is 3 amperes.

If we have three resistors in series with values of 2Ω, 3Ω, and 5Ω, the total resistance (R_total) can be calculated as R_total = R1 + R2 + R3 = 2Ω + 3Ω + 5Ω = 10Ω.

For two resistors in parallel with values of 6Ω and 3Ω, the total resistance can be calculated using the formula 1/R_total = 1/R1 + 1/R2. Therefore, 1/R_total = 1/6 + 1/3 = 1/6 + 2/6 = 3/6. Thus, R_total = 6/3 = 2Ω.

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 find 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.

Consider a series circuit with three resistors: 4Ω, 6Ω, and 10Ω. What is the total resistance? We add the resistances: R_total = 4Ω + 6Ω + 10Ω = 20Ω. Now, let's calculate the total resistance for resistors of 5Ω, 15Ω, and 20Ω.

In a parallel circuit with two resistors of 12Ω and 4Ω, calculate the total resistance. Using the formula, 1/R_total = 1/12 + 1/4. This simplifies to 1/R_total = 1/12 + 3/12 = 4/12, giving R_total = 3Ω. Now, try it with resistors of 8Ω and 2Ω.

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

1. A circuit consists of a 12V battery and two resistors in series: 3Ω and 6Ω. What is the current flowing through the circuit? 2. In a parallel circuit with three resistors of 6Ω, 3Ω, and 2Ω, calculate the total resistance. 3. If the current in a circuit is 5A and the total resistance is 10Ω, 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.

• The sum of individual resistances
• The product of individual resistances
• The average of individual resistances
• Always equal to the largest resistance

Answer: The sum of individual resistances

In a series circuit, the total resistance is calculated by adding all the individual resistances together.

• It increases
• It decreases
• It remains 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: 4A

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

Answer: 10Ω

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

Answer: 18V

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

• All components share the same current
• All components share the same voltage
• Current is divided among components
• Both B and C

Answer: Both B and C

In a parallel circuit, all components share the same voltage, and the current is divided among them.