Ohm's Law - UNSOLVED PRACTICE SET

Q7. State Ohm's Law. Write its mathematical form and explain what each symbol represents.

Q8. Define 1 Ohm of resistance. A student doubles the voltage across a resistor — what happens to the current? (Assume constant temperature.)

Q9. What is a V-I graph? Describe the V-I graph of
(a) an ohmic conductor and
(b) a non-ohmic device like a filament bulb. What does the slope of the V-I graph represent?

Q10. A nichrome wire is connected to a 6 V battery and draws 0.5 A.
(a) Calculate its resistance.
(b) If the wire is replaced with a copper wire of the same dimensions, will the current increase or decrease? Explain.

Q11. What is meant by a 'linear' or 'ohmic' conductor? Give two examples. Why does the filament bulb NOT obey Ohm's Law at high temperatures?

Q12. Explain why Ohm's Law is not a universal law of nature but only applies to certain conductors under certain conditions. What conditions must be maintained?

Q13. State and explain Ohm's Law in detail. Your answer must cover:
(a) the law in words and the formula V = IR,
(b) how to verify Ohm's Law experimentally (circuit diagram description, variables measured, expected graph),
(c) what the slope of the V-I graph represents,
(d) the condition under which Ohm's Law holds (constant temperature), and
(e) two examples of ohmic and two examples of non-ohmic devices with explanations.

Q14. Describe an experiment to verify Ohm's Law for a nichrome wire. Your answer should include:
(a) the circuit diagram description (components: battery, rheostat, ammeter, voltmeter, nichrome wire),
(b) the procedure — how you vary the voltage and record current,
(c) a sample data table format with V and I columns,
(d) how you plot and interpret the V-I graph,
(e) the conclusion drawn from the straight-line graph, and (f) what precaution must be taken regarding the temperature of the wire.

Q15. An electric circuit in an Indian household workshop has a heater of resistance 44 Ω connected to 220 V mains.
(a) Calculate the current drawn.
(b) Using Ohm's Law, verify: if the voltage fluctuates to 200 V, what is the new current?
(c) The heater's resistance increases to 50 Ω when hot. Recalculate current at 220 V.
(d) Does the heater obey Ohm's Law? Explain why resistance increases with temperature.
(e) How does a fuse use the relationship between current and resistance to protect the circuit?

Q16. A resistor is connected to a variable voltage supply. The following readings are obtained:   
V (volts): 2   4   6   8   10   
I (amps): 0.1 0.2 0.3 0.4 0.5
(a) Show that the resistor obeys Ohm's Law by calculating V/I for each reading.
(b) What is the resistance of the resistor?
(c) Plot (or describe) the V-I graph. What is the slope?
(d) If V = 15 V, predict the current.

Q17. Three devices are connected to 230 V mains in separate experiments:   
Device A: current = 2 A   
Device B: current = 0.5 A   

Device C: current = 10 A
(a) Calculate the resistance of each device.
(b) Which device has the highest resistance?
(c) Identify each device as possibly a fan (250 W), a TV (115 W), or an iron (2300 W) by calculating power P = VI.

Q18. A student builds a circuit with a 9 V battery and a 180 Ω resistor.
(a) Calculate the current.
(b) A second identical resistor is added in series — find the new current.
(c) A third identical resistor is added in parallel with the second — describe qualitatively (without full calculation) whether the total current increases or decreases and why.
(d) Which arrangement (series or parallel addition) keeps the current closest to the original?