Calculate the potential difference across a resistor of 12 Ohm... | General Science MCQ | Examoogle

General SciencePhysics: Electricity

Calculate the potential difference across a resistor of 12 Ohm if a current of 2.5 A flows through it, according to Ohm's Law.

30 V

24 V

36 V

4.8 V

Correct Answer

⚙️ TE • Technical Concept & PrincipleGeneral SciencePhysics: Electricity

Option A

30 V

Quick Summary:

The potential difference ( $V$ ) across a resistor is directly proportional to the current ( $I$ ) flowing through it, provided the temperature remains constant. According to Ohm's Law, $V = I \times R$ , where $I = 2.5 \text{ A}$ and $R = 12 \, \Omega$ , resulting in $V = 2.5 \times 12 = 30 \text{ V}$ .

🔬SCScience SolutionConcept & Principle

💡 Explanation

💡 Everyday Analogy (Real-World Intuition)

Think of potential difference as water pressure in a pipe; the resistor is like a narrow section that restricts flow, and the current is the volume of water passing through per second.

🧠 Memory Mnemonic / Shortcut Aid

VIR (V = I $\times R)$ is the classic mnemonic for remembering Ohm's Law.

🔢 Key Formulas

$V = I \times R$ — Ohm's Law relating Voltage, Current, and Resistance

$I = \frac{V}{R}$ — Formula to find current given voltage and resistance

$R = \frac{V}{I}$ — Formula to find resistance given voltage and current

⚙️ Working Principle

Ohm's Law states that the current flowing through a metallic conductor is directly proportional to the potential difference across its terminals. The proportionality constant is the resistance ( $R$ ), which represents the opposition to the flow of charge. In this circuit, the potential difference acts as the 'pressure' pushing the current of $2.5 \text{ A}$ through the $12 \, \Omega$ load.

📌 Key Points

▸
The SI unit of potential difference is the Volt ( $V$ ).
▸
The SI unit of resistance is the Ohm ( $\Omega$ ).
▸
Ohm's Law holds true only for ohmic conductors at a constant temperature.
▸
Current is measured in Amperes ( $A$ ).

✅ Advantages

▸
Simple linear relationship for analysis
▸
Fundamental for basic circuit design

❌ Disadvantages / Limitations

▸
Does not apply to non-ohmic devices like diodes or transistors
▸
Assumes temperature is constant; real resistors heat up and change resistance

🛠️ Applications / Uses

▸
Determining component values in electrical circuits
▸
Safety calculations in household wiring

📄 Additional Information

▸
Constant: The resistance of a conductor is constant if physical conditions such as temperature remain unchanged.
▸
Option B (24 V) is incorrect as $2 \times 12 = 24$ . Option C (36 V) is incorrect as $3 \times 12 = 36$ . Option D (4.8 V) is incorrect as $12 / 2.5 = 4.8$ .

📊 Diagram / Illustration

✅

A is correct — The potential difference is calculated as $V = 2.5 \text{ A} \times 12 \, \Omega = 30 \text{ V}$ .

Core Concepts Used

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Ohm's Law Potential Difference Electrical Resistance

💡 EXAM TIP

Always ensure units are in SI before calculating; if current were given in mA, convert to A first by multiplying by $10^{-3}$ .

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