Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 77 · 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.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 10 hours. How many watt-hours (Wh) are saved?
2. 2.📏 How many milliamperes (mA) make 1 ampere? (a) 60 (b) 10 (c) 1000 (d) 100
3. 3.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
4. 4.⚡ A device works on 24 V and takes 0.25 A. What is its power (in watts)? =
5. 5.🧮 Two resistors in parallel give a total that is … (a) less than either one (b) their sum (c) more than either one (d) always zero
6. 6.🔍 Which is the odd one out? (a) leave fridge door open (b) run fans in empty rooms (c) use LED lamps (d) leave the TV on standby
7. 7.📏 Which unit measures how much a part resists? (a) ampere (A) (b) ohm (Ω) (c) volt (V) (d) watt (W)
8. 8.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 5 % (c) 0 % (d) 25 %
9. 9.🔺 A current of 0.2 A flows when 0.4 V is joined across a resistor. What is its resistance (in ohms)?
10. 10.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
11. 11.🌈 In the resistor colour code, which number does brown stand for?
12. 12.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = I + R (c) V = R ÷ I (d) V = I × R
13. 13.🔺 In the V-I-R triangle, how do we find I? (a) I = V ÷ R (b) I = V × R (c) I = V + R (d) I = R ÷ V
14. 14.⚡ A 24 W device works on 24 V. What current does it take (in amperes)? =
15. 15.True or false: an LDR is a resistance knob. (a) True (b) False
16. 16.🧩 A capacitor in a circuit can … (a) spin a wheel (b) store charge briefly (c) measure heat (d) make light
17. 17.🧮 A 1.1 V battery is joined to 6 Ω and 5 Ω resistors in series. What current flows (in amperes)? =
18. 18.🔺 A current of 0.5 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
19. 19.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3 V supply. What current flows (in mA)?
20. 20.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 6.5 V supply. What current flows (in mA)?
21. 21.💡 A blue LED uses 3 V and should get 10 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
22. 22.🧮 A 100 Ω resistor is joined in series with two equal 10 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
23. 23.🧩 Which component boosts a small signal? (a) resistor (b) LDR (c) LED (d) transistor
24. 24.🧮 Five equal 500 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
25. 25.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
26. 26.🔺 A current of 50 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
27. 27.🔺 A current of 40 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
28. 28.🧩 Which part changes electrical energy into movement? (a) a motor (b) an LED (c) a fuse (d) a resistor
29. 29.🔺 A current of 40 mA flows when 20 V is joined across a resistor. What is its resistance (in ohms)?
30. 30.🔺 A 12 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
31. 31.🔺 A current of 20 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
32. 32.True or false: a diode is a resistance knob. (a) True (b) False
33. 33.🔍 Which is the odd one out? (a) leave fridge door open (b) run fans in empty rooms (c) use daylight to read (d) use old filament bulbs
34. 34.🔺 A current of 40 mA flows when 8 V is joined across a resistor. What is its resistance (in ohms)?
35. 35.🧮 A 50 Ω resistor is joined in series with two equal 330 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
36. 36.🔺 A 20 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
37. 37.⚡ A device works on 9 V and takes 0.25 A. What is its power (in watts)? =
38. 38.🌈 A resistor has the colour bands white, blue, red. What is its value in kilo-ohms (kΩ)? =
39. 39.📏 How many milliamperes (mA) is 0.33 A?
40. 40.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?

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