Solved Examples: Electric Current and Ohm's Law

📚 Quick Study Guide

• ⚡ Electric Current (I): The rate of flow of electric charge. Measured in Amperes (A). Formula: $I = \frac{Q}{t}$, where $Q$ is charge and $t$ is time.
• 🔌 Ohm's Law: States that the voltage across a conductor is directly proportional to the current flowing through it, given constant temperature. Formula: $V = IR$, where $V$ is voltage, $I$ is current, and $R$ is resistance.
• 🚧 Resistance (R): Opposition to the flow of electric current. Measured in Ohms (Ω). Factors affecting resistance: material, length, area, and temperature.
• 💡 Voltage (V): Electric potential difference. Measured in Volts (V). It's the 'push' that drives the current.
• 📏 Resistivity (ρ): A measure of a material's ability to resist electric current. Formula: $R = ρ\frac{L}{A}$, where $L$ is length and $A$ is cross-sectional area.
• 🌡️ Temperature Dependence: Resistance usually increases with temperature for most conductors.

Practice Quiz

1. What is the current flowing through a resistor if a charge of 120 C passes through it in 2 minutes?
   1. A) 0.5 A
   2. B) 1 A
   3. C) 2 A
   4. D) 60 A
2. A resistor has a voltage of 12 V across it and a current of 3 A flowing through it. What is its resistance?
   1. A) 36 Ω
   2. B) 9 Ω
   3. C) 4 Ω
   4. D) 15 Ω
3. If the resistance of a conductor is doubled and the voltage remains constant, what happens to the current?
   1. A) It doubles
   2. B) It halves
   3. C) It remains the same
   4. D) It quadruples
4. What is the unit of resistivity?
   1. A) Ohm (Ω)
   2. B) Ampere (A)
   3. C) Volt (V)
   4. D) Ohm-meter (Ω⋅m)
5. A wire has a resistance of 10 Ω. If its length is doubled and its cross-sectional area is halved, what is the new resistance?
   1. A) 5 Ω
   2. B) 10 Ω
   3. C) 20 Ω
   4. D) 40 Ω
6. What happens to the resistance of most metals as temperature increases?
   1. A) Increases
   2. B) Decreases
   3. C) Remains constant
   4. D) Becomes zero
7. A parallel circuit contains two resistors. Resistor 1 has a value of 4 Ohms and resistor 2 has a value of 8 Ohms. If the Voltage is 24V, what is the total current?
   1. A) 3A
   2. B) 6A
   3. C) 9A
   4. D) 12A