Electric Power

Step 1: Understand the process of starting the auto.

When the auto driver pulls the rope, they are providing mechanical energy to rotate a component in the system. This mechanical energy is converted into electrical energy to generate the initial current required to start the engine. The device responsible for this conversion is a dynamo.

Step 2: Analyze the options.

• (1) Battery: A battery stores electrical energy and does not convert mechanical energy into electrical energy. It provides power to the vehicle once the engine is running.
• (2) Transformer: A transformer is used to change the voltage levels of alternating current (AC) and does not convert mechanical energy into electrical energy.
• (3) Fuse: A fuse is a safety device that protects electrical circuits from excessive current. It does not convert energy from one form to another.
• (4) Dynamo: A dynamo is a device that converts mechanical energy into electrical energy through electromagnetic induction. This is the correct device used in this scenario.

Final Answer: The device used to convert mechanical energy to electrical energy is , which corresponds to option .

Step 1: Recall the definition of potential difference.

The **potential difference** between two points in a circuit is defined as the work done per unit charge in moving a charge from one point to the other. Mathematically, it is given by:

If the charge moved is (a unit positive charge), the work done directly gives the potential difference.

Step 2: Analyze the options.

• (1) Resistivity: Resistivity ( ) is a property of a material that measures how strongly it opposes the flow of electric current. It is not related to the work done in moving a charge.
• (2) Potential difference: This is the correct term for the work done per unit charge in moving a charge from one point to another in a circuit.
• (3) Drift speed: Drift speed is the average velocity of charged particles (e.g., electrons) in a conductor under the influence of an electric field. It is not related to the work done in moving a charge.
• (4) Conductivity: Conductivity ( ) is the reciprocal of resistivity and measures how easily a material allows electric current to flow. It is not related to the work done in moving a charge.

Final Answer: The work done by an electric force in moving a unit positive charge from one point to another in a circuit is called , which corresponds to option .

Correct answer: (i) – (c), (ii) — (a), (iii) – (b)

Explanation:
i) Electric current → Ampere (c)
The SI unit of electric current is the Ampere (A).

ii) Electric charge → Coulomb (a)
The SI unit of electric charge is the Coulomb (C).

iii) Electric potential → Volt (b)
The SI unit of electric potential is the Volt (V).

So, the correct matching is: (i) – (c), (ii) — (a), (iii) – (b).

We are given the following data:
Power of the bulb = 60 W,
Time of operation per day = 3 hours,
Number of days in a month = 30 days.
The energy consumed by the bulb per day is: Since 1 kWh = 1000 Wh, the energy consumed per day in kWh is: The total energy consumed in 30 days is:

The correct option is (B):

Electric power (P) is given by the formula: P = VI

where V is the potential difference (voltage) and I is the current.

So, electric power is the product of current and potential difference.