Technical Science - Term 3 - Week 5

An electrical circuit consists of several key components: a power source (like a battery), conductors (wires), and loads (devices that use electricity, such as bulbs or motors). The power source provides the necessary voltage to push the current through the circuit. Conductors allow the flow of electricity, while loads convert electrical energy into other forms of energy, such as light or motion.

There are two primary types of circuits: series and parallel. In a series circuit, all components are connected end-to-end, meaning the same current flows through each component. If one component fails, the entire circuit is interrupted. In contrast, a parallel circuit has multiple paths for current to flow. If one path is interrupted, current can still flow through other paths, allowing the circuit to remain operational.

Ohm's Law is a fundamental principle in electronics that relates voltage (V), current (I), and resistance (R). It is expressed by the formula V = I × R. This law allows us to calculate the voltage across a component, the current flowing through it, or its resistance, provided we know the other two values. Understanding Ohm's Law is essential for analyzing and designing electrical circuits.

Consider a simple series circuit with a 9V battery and two resistors of 3Ω and 6Ω. To find the total resistance (R_total), we add the resistances: R_total = 3Ω + 6Ω = 9Ω. Using Ohm's Law, we can find the current (I) flowing through the circuit: I = V / R_total = 9V / 9Ω = 1A. Thus, the current flowing through the circuit is 1 ampere.

In a parallel circuit with a 12V battery and two resistors of 4Ω and 12Ω, we first find the total resistance using the formula 1/R_total = 1/R1 + 1/R2. This gives us 1/R_total = 1/4 + 1/12, which simplifies to R_total = 3Ω. Now, applying Ohm's Law: I = V / R_total = 12V / 3Ω = 4A. The total current supplied by the battery is 4 amperes.

Let's work through a problem together. We have a series circuit with a 12V battery and two resistors of 2Ω and 4Ω. First, calculate the total resistance: R_total = 2Ω + 4Ω = 6Ω. Now, apply Ohm's Law to find the current: I = V / R_total = 12V / 6Ω. What is the current flowing through the circuit? (Answer: 2A)

Now, consider a parallel circuit with a 24V battery and two resistors of 6Ω and 3Ω. To find the total resistance, use the formula: 1/R_total = 1/6 + 1/3. Calculate R_total and then find the total current using Ohm's Law. What do you get for the total current? (Answer: 6A)

For independent practice, solve the following problems: 1) A series circuit with a 10V battery and resistors of 5Ω and 5Ω. Calculate the current. 2) A parallel circuit with a 15V battery and resistors of 10Ω and 5Ω. Calculate the total current. Show your work and be prepared to discuss your answers in class.

Design a simple circuit using a 9V battery and at least two resistors of your choice. Calculate the total resistance, current, and voltage across each resistor. Prepare to present your circuit design and calculations to the class.

• Volts
• Amperes
• Ohms
• Watts

Answer: Ohms

Resistance is measured in Ohms, which quantifies how much a component resists the flow of electric current.

• Only that component stops working
• The entire circuit is interrupted
• The current increases
• The voltage drops

Answer: The entire circuit is interrupted

In a series circuit, all components are connected in a single path, so if one fails, the current cannot flow.

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

Answer: V = I × R

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

Answer: A parallel circuit is a type of circuit where multiple components are connected across the same voltage source, allowing current to flow through multiple paths.

In a parallel circuit, if one component fails, the others can still operate, which is a key advantage.

Answer: 2.67Ω

Using the formula 1/R_total = 1/R1 + 1/R2, we find R_total = 1 / (1/4 + 1/8) = 2.67Ω.

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

Answer: It increases

Adding more resistors in series increases the total resistance because the current has to pass through each resistor sequentially.

• 2A
• 5A
• 10A
• 50A