Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 7 · 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 current of 10 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
2. 2.What does a capacitor do? (a) is a resistance knob (b) stores a little charge (c) limits the current (d) lets current go one way
3. 3.🔺 A current of 25 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
4. 4.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 60 Ω resistor? (a) blue-black-brown (b) violet-black-black (c) violet-blue-black (d) blue-black-black
5. 5.🌈 A resistor has the colour bands orange, red, red. What is its value in kilo-ohms (kΩ)? =
6. 6.True or false: a capacitor senses how hot it is. (a) False (b) True
7. 7.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) stays the same (c) gets smaller (d) becomes zero
8. 8.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
9. 9.⚡ Power tells us … (a) the colour of light (b) the size of a cell (c) energy used each second (d) the length of a wire
10. 10.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
11. 11.🔺 A current of 2.5 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
12. 12.💡 A red LED uses 2 V and should get 25 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
13. 13.💡 What does LED stand for? (a) light energy dial (b) low energy device (c) light-emitting diode (d) large electric dial
14. 14.🌈 A resistor has the colour bands orange, black, orange. What is its value (in ohms)?
15. 15.Which of these saves electricity? (a) switch off empty rooms (b) run fans in empty rooms (c) iron one shirt at a time (d) use old filament bulbs
16. 16.Which of these wastes electricity? (a) iron one shirt at a time (b) use daylight to read (c) set the AC to 24 °C (d) unplug idle chargers
17. 17.💡 Does it save or waste electricity to use daylight to read? (a) wastes electricity (b) saves electricity
18. 18.🔺 A current of 10 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
19. 19.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it makes a sound (c) it does not light (d) it changes colour
20. 20.🔺 A current of 0.25 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
21. 21.True or false: current is measured in watts (W). (a) True (b) False
22. 22.🧮 Resistors of 47 Ω, 50 Ω, 47 Ω and 100 Ω are joined in series. What is the total resistance (in ohms)?
23. 23.🔺 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
24. 24.🌈 Which band is read first on a resistor? (a) the one nearest an end (b) the widest gap (c) any band (d) the gold band
25. 25.True or false: energy used each second is measured in watts (W). (a) True (b) False
26. 26.🧮 Two equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
27. 27.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
28. 28.🧮 A 2.6 V battery is joined to 10 Ω and 3 Ω resistors in series. What current flows (in amperes)? =
29. 29.💡 An LED is joined to a 6 V battery through a 1000 Ω resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) does not light (b) lights up (c) may burn out
30. 30.🔺 In the V-I-R triangle, how do we find I? (a) I = V + R (b) I = R ÷ V (c) I = V × R (d) I = V ÷ R
31. 31.🧩 Which component stores a little charge? (a) capacitor (b) fuse (c) resistor (d) LDR
32. 32.🔺 A 12.5 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
33. 33.⚡ A device works on 24 V and takes 0.5 A. What is its power (in watts)? =
34. 34.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
35. 35.What does a motor do? (a) has coloured bands (b) turns a fan or wheels (c) smooths a wobbly supply (d) lets current go one way
36. 36.🧮 Three equal 300 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
37. 37.True or false: the ammeter measures current. (a) False (b) True
38. 38.🔍 Which is the odd one out? (a) use daylight to read (b) use LED lamps (c) leave fridge door open (d) switch off empty rooms
39. 39.🧩 A capacitor in a circuit can … (a) measure heat (b) make light (c) store charge briefly (d) spin a wheel
40. 40.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter

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