Technical Science - Term 2 - Week 9

An electrical circuit consists of several key components: a power source (such as a battery), conductors (wires), and load devices (like resistors, bulbs, or motors). The power source provides the necessary voltage to drive the current through the circuit. Conductors allow the flow of electric charge, while load devices convert electrical energy into other forms of energy, such as light or heat. Understanding these components is crucial for analyzing and designing circuits.

Ohm's Law is a fundamental principle in electrical engineering that relates voltage (V), current (I), and resistance (R) in a circuit. It is expressed as V = I × R. This law allows us to calculate one of the three variables 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.

Consider a series circuit with two resistors: R1 = 4 ohms and R2 = 6 ohms connected to a 12V battery. The total resistance (R_total) in a series circuit is the sum of the individual resistances: R_total = R1 + R2 = 4 + 6 = 10 ohms. Using Ohm's Law, we can find the current: I = V/R_total = 12V / 10 ohms = 1.2 A. Therefore, the current flowing through the circuit is 1.2 amperes.

In a parallel circuit with two resistors, R1 = 4 ohms and R2 = 6 ohms, the total resistance can be calculated using the formula 1/R_total = 1/R1 + 1/R2. Thus, 1/R_total = 1/4 + 1/6 = 3/12 + 2/12 = 5/12. Therefore, R_total = 12/5 = 2.4 ohms. If this circuit is connected to a 12V battery, the total current can be calculated as I_total = V/R_total = 12V / 2.4 ohms = 5 A.

Let's work through a problem together. A circuit has a voltage of 24V and a resistance of 8 ohms. Using Ohm's Law, we need to find the current. First, we apply the formula I = V/R. Substituting the values, we get I = 24V / 8 ohms = 3 A. Now, try to solve a similar problem: What is the current in a circuit with a voltage of 30V and a resistance of 10 ohms?

Now it's your turn to practice independently. Solve the following problems: 1) A circuit has a voltage of 15V and a resistance of 5 ohms. Calculate the current. 2) In a series circuit with three resistors (2 ohms, 3 ohms, and 5 ohms), what is the total resistance? 3) For a parallel circuit with two resistors (4 ohms and 8 ohms), find the total resistance.

• Volts
• Amperes
• Ohms
• Watts

Answer: Ohms

Resistance is measured in ohms, which quantifies how much a material opposes the flow of electric current.

• It doubles
• It halves
• It remains the same
• It quadruples

Answer: It doubles

According to Ohm's Law, if voltage increases while resistance stays the same, current will also increase proportionally.

Answer: Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance.

This law is fundamental in understanding how voltage, current, and resistance interact in electrical circuits.

• 2 ohms
• 5 ohms
• 8 ohms
• 15 ohms

Answer: 8 ohms

In a series circuit, total resistance is the sum of individual resistances: R_total = R1 + R2 = 3 + 5 = 8 ohms.

• It increases
• It decreases
• It remains the same
• It becomes infinite

Answer: It increases

If one resistor in a parallel circuit fails, the overall resistance increases because there are fewer pathways for current to flow.

Answer: 5 A

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