Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 82 · 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.Which of these saves electricity? (a) run fans in empty rooms (b) use old filament bulbs (c) switch off empty rooms (d) leave fridge door open
2. 2.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) gets bigger (c) becomes zero (d) stays the same
3. 3.🔺 A current of 1 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
4. 4.💡 Does it save or waste electricity to use old filament bulbs? (a) saves electricity (b) wastes electricity
5. 5.🔺 A current of 0.2 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
6. 6.📏 How many milliamperes (mA) is 2.26 A?
7. 7.True or false: a thermistor smooths a wobbly supply. (a) False (b) True
8. 8.True or false: the ammeter is joined in series. (a) False (b) True
9. 9.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) smaller (c) zero (d) stay the same
10. 10.🌈 A resistor has the colour bands brown, brown, red. What is its value in kilo-ohms (kΩ)? =
11. 11.📏 How many milliamperes (mA) is 1.91 A?
12. 12.True or false: to run fans in empty rooms saves electricity. (a) False (b) True
13. 13.🔍 Which is the odd one out? (a) leave fridge door open (b) run fans in empty rooms (c) use old filament bulbs (d) switch off empty rooms
14. 14.🌈 A gold fourth band on a resistor means the value may be off by … (a) 0 % (b) 50 % (c) 25 % (d) 5 %
15. 15.What does an LDR do? (a) lets current go one way (b) senses how bright it is (c) blows if current is high (d) senses how hot it is
16. 16.🔺 A current of 0.25 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
17. 17.🧮 Three equal 300 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
18. 18.True or false: an LDR stores a little charge. (a) False (b) True
19. 19.⚡ A device works on 1.5 V and takes 1 A. What is its power (in watts)? =
20. 20.True or false: how much a part resists is measured in ohms (Ω). (a) True (b) False
21. 21.📏 How many amperes (A) is 2400 mA? =
22. 22.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
23. 23.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
24. 24.⚡ A 36 W device works on 12 V. What current does it take (in amperes)? =
25. 25.🌈 A resistor has the colour bands yellow, yellow, orange. What is its value (in ohms)?
26. 26.🌈 A resistor has the colour bands yellow, green, brown. What is its value (in ohms)?
27. 27.⚡ A device works on 6 V and takes 3 A. What is its power (in watts)? =
28. 28.True or false: a buzzer blows if current is high. (a) False (b) True
29. 29.📏 How many watts (W) is 0.3 kW?
30. 30.💡 Does it save or waste electricity to leave the TV on standby? (a) wastes electricity (b) saves electricity
31. 31.🌈 A resistor has the colour bands brown, black, orange. What is its value (in ohms)?
32. 32.🌈 In the resistor colour code, which number does red stand for?
33. 33.🧮 Resistors of 470 Ω and 220 Ω are joined in series. What is the total resistance (in ohms)?
34. 34.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3 V supply. What current flows (in mA)?
35. 35.🧮 Two resistors in parallel give a total that is … (a) their sum (b) more than either one (c) always zero (d) less than either one
36. 36.📏 Which unit measures voltage? (a) ohm (Ω) (b) volt (V) (c) ampere (A) (d) watt (W)
37. 37.🌈 A resistor has the colour bands violet, red, brown. What is its value (in ohms)?
38. 38.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
39. 39.🌈 A resistor has the colour bands red, green, orange. What is its value (in ohms)?
40. 40.⚡ A device works on 3 V and takes 0.25 A. What is its power (in watts)? =

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