Physics - Term 2 - Week 8

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. Understanding this law is crucial for analyzing electric circuits, as it allows us to calculate the current, voltage, or resistance when the other two quantities are known.

In a series circuit, components are connected end-to-end, so the same current flows through each component. The total resistance in a series circuit is the sum of the individual resistances (R_total = R1 + R2 + ... + Rn). 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 predicting how circuits behave under different conditions.

Suppose we have 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. Plugging in the values, we get I = 12V / 4Ω = 3A. Therefore, the current flowing through the circuit is 3 amperes.

Consider a series circuit with three resistors: R1 = 2Ω, R2 = 3Ω, and R3 = 5Ω. To find the total resistance, we add the resistances together: R_total = R1 + R2 + R3 = 2Ω + 3Ω + 5Ω = 10Ω. Thus, the total resistance in the series circuit is 10 ohms.

Let's work through a problem together. A circuit has a voltage of 24 volts and a resistance of 6 ohms. Using Ohm's Law, calculate the current. Students should apply the formula I = V/R. After calculating, we find I = 24V / 6Ω = 4A. Discuss how changing the resistance would affect the current.

Now, let's find the total resistance of a parallel circuit with two resistors: R1 = 4Ω and R2 = 12Ω. Use the formula 1/R_total = 1/R1 + 1/R2. Students should calculate 1/R_total = 1/4 + 1/12. After finding a common denominator and solving, we get R_total = 3Ω. Discuss the implications of adding more resistors in parallel.

Students will complete a worksheet with various problems involving Ohm's Law and circuit configurations. Problems will include calculating current, voltage, and resistance in both series and parallel circuits. Encourage students to show their work and explain their reasoning for each step.

Students will research a real-world application of electric circuits, such as household wiring or electronic devices. They will write a short report explaining how Ohm's Law and circuit configurations apply to their chosen example, including any calculations relevant to their analysis.

• 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 resistance.

• Always less than the smallest resistor
• The sum of all resistances
• The product of all resistances
• Equal to the largest resistor

Answer: The sum of all resistances

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

Answer: 2A

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

• It increases
• It decreases
• It stays the same
• It doubles

Answer: It decreases

Adding more resistors in parallel decreases the total resistance because there are more paths for current to flow.

Answer: 2Ω

Using the formula 1/R_total = 1/R1 + 1/R2, we find 1/R_total = 1/6 + 1/3 = 1/2, thus R_total = 2Ω.

• It halves
• It doubles
• It stays the same
• It quadruples

Answer: It doubles

According to Ohm's Law, if voltage increases while resistance remains constant, current will also increase proportionally.

Answer: In series circuits, current flows through each component sequentially, while in parallel circuits, components are connected across the same voltage source, allowing multiple paths for current.