Technical Science - Term 4 - Week 5

An electrical circuit is a closed loop that allows electric 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 current is driven by voltage, which is the potential difference between two points in a circuit.

Ohm's Law is a fundamental principle in electronics that relates voltage (V), current (I), and resistance (R) in a circuit. The formula is V = I × R. This law allows us to calculate one of these values if the other two are known. For example, if a circuit has a voltage of 12 volts and a resistance of 4 ohms, the current can be calculated as I = V/R, which equals 3 amperes.

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, a parallel circuit has components connected across the same voltage source, allowing multiple paths for current. The total resistance in a parallel circuit is found using the formula 1/R_total = 1/R1 + 1/R2 + ... + 1/Rn.

Consider a circuit with a voltage of 24 volts and a resistance of 6 ohms. To find the current, we use Ohm's Law: I = V/R. Substituting the values, we get I = 24V / 6Ω = 4A. This means the circuit carries a current of 4 amperes.

If we have three resistors in series: R1 = 2Ω, R2 = 3Ω, and R3 = 5Ω, the total resistance (R_total) 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 = 4Ω and R2 = 6Ω, we calculate the total resistance using the formula 1/R_total = 1/R1 + 1/R2. Thus, 1/R_total = 1/4 + 1/6. Finding a common denominator (12), we get 1/R_total = 3/12 + 2/12 = 5/12. Therefore, R_total = 12/5 = 2.4Ω.

Let's work together on a problem. A circuit has a voltage of 30 volts and a resistance of 10 ohms. What is the current? Using Ohm's Law, we can calculate I = V/R = 30V / 10Ω = 3A. Now, try calculating the current for a circuit with 50 volts and 25 ohms.

Look at the following circuit diagram. Identify whether the resistors are in series or parallel. Discuss with your partner how you determined your answer. Remember, in series, the current is the same through all components, while in parallel, the voltage across each component is the same.

Calculate the total resistance for the following series circuit: R1 = 5Ω, R2 = 10Ω, and R3 = 15Ω. Add the resistances together: R_total = R1 + R2 + R3 = 5Ω + 10Ω + 15Ω = 30Ω. Now, try a similar problem with different values.

Complete the worksheet provided, which includes various circuits where you need to calculate the current, voltage, or resistance using Ohm's Law. Ensure you show all your workings for full credit.

Design a simple circuit using at least three resistors. Calculate the total resistance and the current if the voltage supply is 12 volts. Present your design and calculations to the class.

Write a short paragraph reflecting on the differences between series and parallel circuits. Include examples of where you might use each type in real-world applications.

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

Answer: V = I × R

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

• Less than the smallest resistor
• The sum of all resistors
• The same as the largest resistor
• Zero

Answer: The sum of all resistors

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

• It decreases
• It stays the same
• It increases
• It becomes zero

Answer: It increases

Adding more branches in a parallel circuit allows more paths for current to flow, increasing the total current.

Answer: 4A

Using Ohm's Law: I = V/R = 60V / 15Ω = 4A.

• Capacitor
• Inductor
• Resistor
• Battery

Answer: Resistor

A resistor is specifically designed to oppose the flow of electric current.

Answer: 2Ω

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

• Volts
• Amperes
• Ohms
• Watts

Answer: Ohms

The unit of electrical resistance is the ohm (Ω).