Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 59 · 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.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
2. 2.🧮 Two resistors in parallel give a total that is … (a) their sum (b) less than either one (c) always zero (d) more than either one
3. 3.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) stay the same (c) bigger (d) zero
4. 4.💡 Does it save or waste electricity to close the fridge quickly? (a) saves electricity (b) wastes electricity
5. 5.🔺 A current of 0.5 A flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
6. 6.True or false: an LED boosts a small signal. (a) False (b) True
7. 7.⚡ Which formula gives electric power? (a) P = V × I (b) P = V + I (c) P = I ÷ V (d) P = V ÷ I
8. 8.🔺 A current of 0.25 A flows when 1.25 V is joined across a resistor. What is its resistance (in ohms)?
9. 9.🧮 Five equal 250 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
10. 10.True or false: on an LED, the round-side leg is the cathode (−). (a) False (b) True
11. 11.⚡ Power tells us … (a) the size of a cell (b) the length of a wire (c) the colour of light (d) energy used each second
12. 12.📏 How many milliamperes (mA) is 2.64 A?
13. 13.🧩 Which part changes electrical energy into movement? (a) an LED (b) a motor (c) a fuse (d) a resistor
14. 14.🌈 A resistor has the colour bands blue, grey, yellow. What is its value in kilo-ohms (kΩ)? =
15. 15.🌈 In the resistor colour code, which number does red stand for?
16. 16.🧮 Two equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
17. 17.🧮 An 18 V battery is joined to 12 Ω and 6 Ω resistors in series. What current flows (in amperes)? =
18. 18.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 4 V supply. What current flows (in mA)?
19. 19.📏 How many milliamperes (mA) is 0.53 A?
20. 20.💡 What does LED stand for? (a) light energy dial (b) light-emitting diode (c) low energy device (d) large electric dial
21. 21.💡 An LED is joined to a 5 V battery with no resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) does not light (b) may burn out (c) lights up
22. 22.🔺 A current of 1 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
23. 23.💡 Does it save or waste electricity to unplug idle chargers? (a) saves electricity (b) wastes electricity
24. 24.🧮 A 1.6 V battery is joined to 4 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
25. 25.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 8 hours. How many watt-hours (Wh) are saved?
26. 26.💡 A red LED uses 2 V and should get 10 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
27. 27.🔺 A current of 0.5 A flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
28. 28.🌈 Which band is read first on a resistor? (a) the widest gap (b) the gold band (c) any band (d) the one nearest an end
29. 29.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
30. 30.What does a diode do? (a) stores a little charge (b) turns a fan or wheels (c) glows using little power (d) lets current go one way
31. 31.💡 An LED is joined to a 6 V battery through a 330 Ω resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) lights up (b) does not light (c) may burn out
32. 32.🌈 A resistor has the colour bands green, brown, red. What is its value in kilo-ohms (kΩ)? =
33. 33.📏 Which unit measures how much a part resists? (a) ohm (Ω) (b) watt (W) (c) ampere (A) (d) volt (V)
34. 34.📏 Which unit measures power? (a) watt (W) (b) ampere (A) (c) volt (V) (d) ohm (Ω)
35. 35.True or false: to use old filament bulbs saves electricity. (a) False (b) True
36. 36.True or false: a capacitor glows using little power. (a) True (b) False
37. 37.🔺 In the V-I-R triangle, how do we find V? (a) V = I + R (b) V = R ÷ I (c) V = I × R (d) V = I ÷ R
38. 38.🌈 In the resistor colour code, which number does grey stand for?
39. 39.True or false: to switch off empty rooms saves electricity. (a) False (b) True
40. 40.What does a potentiometer do? (a) boosts a small signal (b) limits the current (c) is a resistance knob (d) stores a little charge

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