Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 78 · 40 questions

Remember (Find the topic, use the formula): Find the topic and the formula: V = I × R, I = V ÷ R, R = V ÷ I, P = V × I, units = W × h ÷ 1000. Change mA to A and kΩ to Ω before using a formula. Check: put your answer back into the formula.

1. 1.🧮 Resistors of 33 Ω, 33 Ω and 100 Ω are joined in series. What is the total resistance (in ohms)?
2. 2.⚡ A device works on 1.5 V and takes 0.1 A. What is its power (in watts)? =
3. 3.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = V ÷ I (c) R = V + I (d) R = I ÷ V
4. 4.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 3.5 V supply. What current flows (in mA)?
5. 5.🧮 Resistors of 100 Ω, 68 Ω and 150 Ω are joined in series. What is the total resistance (in ohms)?
6. 6.🧩 Which part changes electrical energy into movement? (a) a resistor (b) an LED (c) a fuse (d) a motor
7. 7.🔺 In the V-I-R triangle, how do we find I? (a) I = V ÷ R (b) I = V + R (c) I = R ÷ V (d) I = V × R
8. 8.What does a resistor do? (a) makes things spin (b) makes a beeping sound (c) beeps for an alarm (d) has coloured bands
9. 9.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
10. 10.⚡ Which formula gives electric power? (a) P = V + I (b) P = V ÷ I (c) P = I ÷ V (d) P = V × I
11. 11.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 9 hours. How many watt-hours (Wh) are saved?
12. 12.🧩 Which component blows if current is high? (a) resistor (b) potentiometer (c) thermistor (d) fuse
13. 13.📏 How many kilo-ohms (kΩ) is 2900 Ω? =
14. 14.💡 Does it save or waste electricity to leave the TV on standby? (a) wastes electricity (b) saves electricity
15. 15.🔺 A current of 0.2 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
16. 16.🔺 A current of 2 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
17. 17.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
18. 18.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
19. 19.🧾 Which lamp gives the same light for the least power? (a) an oil lamp (b) an LED lamp (c) a filament bulb (d) a candle
20. 20.💡 An LED is joined to a 5 V battery with no resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) does not light (b) may burn out (c) lights up
21. 21.🔺 A current of 25 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
22. 22.🌈 A resistor has the colour bands white, yellow, red. What is its value in kilo-ohms (kΩ)? =
23. 23.🌈 Which band is read first on a resistor? (a) the one nearest an end (b) any band (c) the widest gap (d) the gold band
24. 24.🔍 Which is the odd one out? (a) use daylight to read (b) use old filament bulbs (c) iron one shirt at a time (d) leave fridge door open
25. 25.🔺 A current of 20 mA flows when 6.6 V is joined across a resistor. What is its resistance (in ohms)?
26. 26.⚡ Power tells us … (a) energy used each second (b) the length of a wire (c) the colour of light (d) the size of a cell
27. 27.🧩 A capacitor in a circuit can … (a) store charge briefly (b) spin a wheel (c) measure heat (d) make light
28. 28.🧾 A family uses 60 units of electricity in a month and each unit costs ₹9. What is the bill (in ₹)?
29. 29.📏 How many watts (W) is 3 kW?
30. 30.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
31. 31.📏 Which unit measures power? (a) watt (W) (b) ampere (A) (c) ohm (Ω) (d) volt (V)
32. 32.🧮 Two resistors in parallel give a total that is … (a) their sum (b) always zero (c) more than either one (d) less than either one
33. 33.📏 How many watts (W) is 4.3 kW?
34. 34.⚡ A device works on 5 V and takes 0.5 A. What is its power (in watts)? =
35. 35.🌈 A resistor has the colour bands grey, green, orange. What is its value (in ohms)?
36. 36.🔺 A current of 25 mA flows when 6.25 V is joined across a resistor. What is its resistance (in ohms)?
37. 37.🔺 A current of 25 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
38. 38.🔺 A current of 10 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
39. 39.🔺 A 1.5 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
40. 40.🔺 A current of 10 mA flows when 5 V is joined across a resistor. What is its resistance (in ohms)?

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