- Define electric current. State its SI unit.
- What is meant by an electric circuit? Draw a diagram of a simple circuit comprising a battery, a
bulb, an ammeter, and a plug key.
- Calculate the number of electrons constituting one coulomb of charge. (Charge of 1 electron = $1.6
\times 10^{-19}$ C).
- A current of 0.5 A is drawn by a filament of an electric bulb for 10 minutes. Find the amount of
electric charge that flows through the circuit.
- How is the direction of electric current related to the flow of electrons?
- What is the function of the cell or battery in an electric circuit?
- Define one Ampere.
- Name the instrument used to measure electric current. How is it connected in a circuit?
- What makes the electric charge flow through a conductor?
- If $10^{20}$ electrons flow through a conductor in 1 second, calculate the current.
- What is the difference between an open circuit and a closed circuit?
- Is electric current a scalar or vector quantity? Explain briefly.
- Which particles constitute electric current in metallic conductors?
- Define quantization of charge.
- A charge of 60 C flows through a wire in 2 minutes. What is the current flowing in the wire?
- Define electric potential difference. Name the device used to measure it.
- State Ohm's Law. Draw a circuit diagram to verify it experimentally.
- How much work is done in moving a charge of 3 C across two points having a potential difference 15
V?
- Define 1 Volt.
- What holds the electrons in an atom? Why do conductors conduct electricity?
- What is the shape of the V-I graph for an Ohmic conductor? What does its slope represent?
- A heater of resistance 50 $\Omega$ is connected to 220 V supply. Calculate the current drawn by it.
- How does the V-I graph look for a non-ohmic conductor? Give one example.
- If the potential difference across a wire is doubled, how does the current through it change
(assuming temperature is constant)?
- Why is the voltmeter always connected in parallel across the circuit component?
- What is the resistance of an ideal voltmeter?
- Two points A and B are at potentials 100 V and -10 V respectively. Find the work done in moving 5 C
charge from B to A.
- Does Ohm's law hold good for all circuit elements? Name two for which it fails.
- Explain why the temperature of a conductor rises when current flows through it.
- A 12 V battery is connected across an unknown resistor. There is a current of 2.5 mA in the circuit.
Find the value of the resistance.
- List the factors on which the resistance of a conductor depends.
- Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal?
- A wire of length $L$ and resistance $R$ is stretched to make it twice as long. What is its new
resistance?
- Derive the expression for the equivalent resistance of three resistors connected in series.
- Derive the expression for the equivalent resistance of three resistors connected in parallel.
- Why is the series arrangement not used for domestic circuits?
- Two resistors of 10 $\Omega$ ar connected in parallel. What is the equivalent resistance?
- A piece of wire of resistance $R$ is cut into five equal parts. These parts are then connected in
parallel. If the equivalent resistance of this combination is $R'$, find the ratio $R/R'$.
- Calculate the resistivity of a material of wire 1 m long, 0.4 mm diameter and having a resistance of
2 $\Omega$.
- Differentiate between resistance and resistivity.
- Which has higher resistance: a 100 W bulb or a 60 W bulb? (Rated at same voltage).
- Three resistors 2 $\Omega$, 3 $\Omega$, and 6 $\Omega$ are connected in parallel. Calculate
aggregate resistance.
- In a series circuit, if one component fails, what happens to the others?
- Show how you would connect three resistors, each of resistance 6 $\Omega$, so that the combination
has a resistance of (i) 9 $\Omega$, (ii) 4 $\Omega$.
- The resistivity of copper is $1.62 \times 10^{-8} \Omega$ m. What does this statement mean?
- State Joule’s law of heating.
- Explain why the cord of an electric heater does not glow while the heating element does.
- Compute the heat generated while transferring 96000 coulomb of charge in one hour through a
potential difference of 50 V.
- An electric iron consumes energy at a rate of 840 W when heating is at the maximum rate and 360 W
when the heating is at the minimum. The voltage is 220 V. What are the current and the resistance in
each case?
- What determines the rate at which energy is delivered by a current?
- An electric motor takes 5 A from a 220 V line. Determine the power of the motor and energy consumed
in 2 h.
- What is the commercial unit of electrical energy? Convert it into Joules.
- Why are copper and aluminum wires usually employed for electricity transmission?
- Which uses more energy, a 250 W TV set in 1 hr, or a 1200 W toaster in 10 minutes?
- Explain the principle of an electric fuse. How is it rated?
- A bulb is rated 220V, 100W. What is its resistance?
- Two conducting wires of the same material and of equal lengths and equal diameters are first
connected in series and then parallel in a circuit across the same potential difference. Find the
ratio of heat produced in series and parallel.
- Heat produced in a resistor is directly proportional to the square of current. Why?
- Name the gas filled in electric bulbs. Why is it used?
- An electric refrigerator rated 400 W operates 8 hours/day. What is the cost of energy to operate it
for 30 days at Rs 3.00 per kWh?
