Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 86 · 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 24 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
2. 2.🧮 A 20 Ω resistor is joined in series with two equal 20 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
3. 3.True or false: on an LED, the leg by the flat edge is the anode (+). (a) True (b) False
4. 4.What does a thermistor do? (a) makes a beeping sound (b) has coloured bands (c) turns a fan or wheels (d) senses how hot it is
5. 5.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 watt (c) 1 kilowatt-hour (kWh) (d) 1 ampere
6. 6.🔺 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
7. 7.🧮 Four equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
8. 8.⚡ A device works on 1.5 V and takes 0.25 A. What is its power (in watts)? =
9. 9.🌈 A resistor has the colour bands grey, orange, red. What is its value in kilo-ohms (kΩ)? =
10. 10.Which of these wastes electricity? (a) use daylight to read (b) close the fridge quickly (c) run fans in empty rooms (d) switch off empty rooms
11. 11.🌈 In the resistor colour code, which number does red stand for?
12. 12.⚡ A device works on 1.5 V and takes 0.1 A. What is its power (in watts)? =
13. 13.⚡ Which formula gives electric power? (a) P = V × I (b) P = I ÷ V (c) P = V + I (d) P = V ÷ I
14. 14.🌈 A resistor has the colour bands orange, yellow, black. What is its value (in ohms)?
15. 15.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
16. 16.🌈 A resistor has the colour bands yellow, orange, red. What is its value in kilo-ohms (kΩ)? =
17. 17.🧾 Which lamp gives the same light for the least power? (a) an oil lamp (b) a candle (c) a filament bulb (d) an LED lamp
18. 18.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) gets smaller (c) becomes zero (d) gets bigger
19. 19.🌈 In the resistor colour code, which number does black stand for?
20. 20.True or false: the voltmeter measures voltage. (a) False (b) True
21. 21.🔺 A current of 3 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
22. 22.🧩 Which component blows if current is high? (a) resistor (b) diode (c) motor (d) fuse
23. 23.🧮 Resistors of 22 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
24. 24.True or false: the voltmeter measures current. (a) True (b) False
25. 25.🧮 Three equal 150 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
26. 26.🌈 A resistor has the colour bands blue, violet, brown. What is its value (in ohms)?
27. 27.🧮 Three equal 15 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
28. 28.True or false: a buzzer limits the current. (a) False (b) True
29. 29.🧩 Which component stores a little charge? (a) LDR (b) capacitor (c) fuse (d) LED
30. 30.🔍 Which is the odd one out? (a) close the fridge quickly (b) run fans in empty rooms (c) leave the TV on standby (d) use old filament bulbs
31. 31.True or false: to use LED lamps saves electricity. (a) True (b) False
32. 32.🔺 A 1.5 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
33. 33.🔺 A current of 1.5 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
34. 34.True or false: on an LED, the shorter leg is the cathode (−). (a) False (b) True
35. 35.🔍 Which is the odd one out? (a) close the fridge quickly (b) leave fridge door open (c) switch off empty rooms (d) use LED lamps
36. 36.🧾 A 250 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
37. 37.What does a buzzer do? (a) senses how bright it is (b) lets current go one way (c) turns a fan or wheels (d) makes a beeping sound
38. 38.🌈 A resistor has the colour bands red, red, red. What is its value (in ohms)?
39. 39.🧮 A 150 Ω resistor is joined in series with two equal 20 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
40. 40.What does a motor do? (a) makes things spin (b) smooths a wobbly supply (c) senses how hot it is (d) stores a little charge

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