Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 659 · 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.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
2. 2.True or false: resistance is measured in watts (W). (a) False (b) True
3. 3.🔺 A current of 25 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
4. 4.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = I + R (c) V = I × R (d) V = R ÷ I
5. 5.True or false: to leave fridge door open wastes electricity. (a) False (b) True
6. 6.⚡ A 0.15 W device works on 1.5 V. What current does it take (in amperes)? =
7. 7.🧮 Two equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
8. 8.📏 How many milliamperes (mA) make 1 ampere? (a) 100 (b) 60 (c) 10 (d) 1000
9. 9.🧩 Which part changes electrical energy into movement? (a) a motor (b) a resistor (c) a fuse (d) an LED
10. 10.True or false: the ammeter is joined in series. (a) True (b) False
11. 11.Which of these wastes electricity? (a) use daylight to read (b) close the fridge quickly (c) switch off empty rooms (d) iron one shirt at a time
12. 12.🔺 A current of 1.5 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
13. 13.True or false: to iron one shirt at a time saves electricity. (a) False (b) True
14. 14.📏 Which unit measures the flow of charge? (a) ohm (Ω) (b) ampere (A) (c) watt (W) (d) volt (V)
15. 15.🔺 A current of 10 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
16. 16.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 5 hours. How many watt-hours (Wh) are saved?
17. 17.📏 In the water-pipe picture of a circuit, resistance is like … (a) the water pressure (b) a narrow pipe (c) a bigger tank (d) the flow of water
18. 18.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 810 Ω resistor? (a) grey-brown-black (b) grey-brown-red (c) brown-grey-brown (d) grey-brown-brown
19. 19.⚡ A 2.4 W device works on 12 V. What current does it take (in amperes)? =
20. 20.💡 Does it save or waste electricity to use old filament bulbs? (a) saves electricity (b) wastes electricity
21. 21.🔺 A 24 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
22. 22.🧾 A 500 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
23. 23.🔺 A current of 20 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
24. 24.🔺 A current of 0.5 A flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
25. 25.💡 A blue LED uses 3 V and should get 10 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
26. 26.🧩 Which component makes a beeping sound? (a) LED (b) buzzer (c) fuse (d) resistor
27. 27.🌈 A resistor has the colour bands red, blue, brown. What is its value (in ohms)?
28. 28.True or false: on an LED, the round-side leg is the cathode (−). (a) False (b) True
29. 29.🔺 A current of 10 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
30. 30.⚡ A device works on 6 V and takes 0.2 A. What is its power (in watts)? =
31. 31.🔺 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
32. 32.🌈 In the resistor colour code, which number does red stand for?
33. 33.📏 How many kilo-ohms (kΩ) is 5600 Ω? =
34. 34.🧾 A 1500 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
35. 35.🧮 Five equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
36. 36.🧮 Two resistors in parallel give a total that is … (a) always zero (b) their sum (c) less than either one (d) more than either one
37. 37.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 78000 Ω resistor? (a) grey-violet-orange (b) violet-grey-orange (c) violet-grey-yellow (d) violet-grey-red
38. 38.🧮 An 18 V battery is joined to 8 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
39. 39.🔺 A current of 3 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
40. 40.🔺 A 4.8 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?

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