Electric Charge And Electric Current — Important Questions

5 A

Step 1: The formula for electric current is I = q / t. Step 2: Here, q = 25 C (charge) and t = 5 s (time). Step 3: So, I = 25 / 5 = 5 A. Step 4: The unit of current is ampere (A), where 1 A = 1 C/s. Step 5: Option 0.2 A would be wrong because that is t/q, not q/t — a common mistake to avoid.

Ammeter

Step 1: An ammeter is the instrument designed specifically to measure electric current. Step 2: It is always connected in series in a circuit so that the same current flows through it. Step 3: A voltmeter measures potential difference (voltage) and is connected in parallel. Step 4: A thermometer measures temperature, not current. Step 5: A galvanometer can detect very small currents but is not the standard instrument for measuring current in normal circuits.

The work done by the source to drive one unit charge around the complete circuit

Step 1: EMF stands for Electromotive Force, represented by the symbol ε. Step 2: It is defined as the work done (W) by the electrical energy source in driving one unit of charge (q) around the complete circuit. Step 3: Formula: ε = W / q. Step 4: The SI unit of EMF is volts (V) or joules per coulomb (J/C). Step 5: A battery is like a water pump — it 'pushes' the charges to flow, and EMF is a measure of that pushing ability.

In parallel with the bulb

Step 1: A voltmeter measures the potential difference (voltage) across a component. Step 2: To measure the voltage across any component, the voltmeter must be connected in parallel — meaning it is connected across the two terminals of the component. Step 3: When connected in parallel, both the voltmeter and the bulb experience the same potential difference. Step 4: An ammeter, on the other hand, is connected in series. Step 5: Remember: Voltmeter → Parallel; Ammeter → Series.