Physics - Term 2 - 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 the behavior of these components is crucial for analyzing how circuits function.

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 values of voltage, current, and resistance in 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 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 analysis.

Consider a circuit with a voltage of 12 volts and a resistance of 4 ohms. To find the current, we can use Ohm's Law: I = V/R. Substituting the values, we get I = 12V / 4Ω = 3A. Therefore, 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 can be calculated as R_total = R1 + R2 + R3 = 2Ω + 3Ω + 5Ω = 10Ω. This means the total resistance in the circuit is 10 ohms.

For two resistors in parallel with values of 6Ω and 3Ω, we can find 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. 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 30 volts and 10 ohms of resistance.

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

In a parallel circuit with resistors of 12Ω and 4Ω, calculate the total resistance. Using the formula, 1/R_total = 1/12 + 1/4 = 1/12 + 3/12 = 4/12. Thus, R_total = 12/4 = 3Ω. Now, try calculating the total resistance if we add a 6Ω resistor in parallel.

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

1. A circuit has a voltage of 48 volts and consists of two resistors in series: 10Ω and 20Ω. Calculate the current flowing through the circuit. 2. In a parallel circuit with three resistors of 8Ω, 4Ω, and 2Ω, find the total resistance. 3. If a circuit has a total resistance of 12Ω and a current of 3A, what is the voltage?

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

Answer: V = I × R

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

• Always less than the smallest resistor
• The sum of all resistances
• The product of all resistances
• Independent of the number of resistors

Answer: The sum of all resistances

In a series circuit, the total resistance is calculated by adding all 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: 2Ω

Using the formula 1/R_total = 1/6 + 1/3, we find R_total = 2Ω.

• 5Ω
• 20Ω
• 10Ω
• 15Ω

Answer: 5Ω

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

• Current is the same through all components
• Voltage is the same across all components
• Total resistance is less than the smallest resistor
• Total current is the sum of individual currents

Answer: Current is the same through all components