Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 639 · 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.📏 How many watts (W) is 2.6 kW?
2. 2.📏 How many milliamperes (mA) is 2.55 A?
3. 3.What does a buzzer do? (a) senses how hot it is (b) beeps for an alarm (c) has coloured bands (d) glows using little power
4. 4.🔺 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
5. 5.💡 A red LED uses 2 V and should get 25 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
6. 6.💡 An LED is joined to a 9 V battery through a 1000 Ω resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) may burn out (b) does not light (c) lights up
7. 7.🔺 A 16 V supply is joined across a 400 Ω resistor. What current flows (in milliamperes, mA)?
8. 8.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 1200 Ω resistor? (a) red-brown-red (b) brown-red-red (c) brown-red-brown (d) brown-red-orange
9. 9.True or false: the ammeter measures current. (a) False (b) True
10. 10.What does an LDR do? (a) makes things spin (b) boosts a small signal (c) senses how bright it is (d) has coloured bands
11. 11.🧮 Four equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
12. 12.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
13. 13.True or false: to use old filament bulbs wastes electricity. (a) True (b) False
14. 14.🧮 Resistors of 33 Ω, 220 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
15. 15.🔺 A 2 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
16. 16.🧮 Two resistors in parallel give a total that is … (a) less than either one (b) their sum (c) more than either one (d) always zero
17. 17.💡 A red LED uses 2 V and should get 20 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
18. 18.⚡ Power tells us … (a) the colour of light (b) energy used each second (c) the length of a wire (d) the size of a cell
19. 19.🧩 Which part changes electrical energy into sound? (a) a resistor (b) a capacitor (c) a buzzer (d) a diode
20. 20.True or false: the ammeter is joined across a part. (a) True (b) False
21. 21.True or false: on an LED, the shorter leg is the cathode (−). (a) False (b) True
22. 22.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) stays the same (c) becomes zero (d) gets smaller
23. 23.🧩 A capacitor in a circuit can … (a) spin a wheel (b) store charge briefly (c) measure heat (d) make light
24. 24.🔺 A 20 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
25. 25.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 25 % (c) 5 % (d) 0 %
26. 26.🌈 Which band is read first on a resistor? (a) the gold band (b) the one nearest an end (c) the widest gap (d) any band
27. 27.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
28. 28.🧮 Three equal 30 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
29. 29.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
30. 30.True or false: a motor makes things spin. (a) True (b) False
31. 31.Which of these is measured in volts (V)? (a) how much a part resists (b) power (c) voltage (d) energy used each second
32. 32.True or false: a potentiometer lets current go one way. (a) False (b) True
33. 33.📏 How many amperes (A) is 1760 mA? =
34. 34.💡 Does it save or waste electricity to leave fridge door open? (a) saves electricity (b) wastes electricity
35. 35.True or false: the ammeter is joined in series. (a) False (b) True
36. 36.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 5000 Ω resistor? (a) green-black-red (b) green-black-orange (c) green-black-brown (d) blue-green-red
37. 37.📏 Voltmeter or ammeter: which one is joined in series? (a) ammeter (b) voltmeter
38. 38.🔺 In the V-I-R triangle, how do we find R? (a) R = I ÷ V (b) R = V + I (c) R = V ÷ I (d) R = V × I
39. 39.🔺 A current of 2.5 A flows when 20 V is joined across a resistor. What is its resistance (in ohms)?
40. 40.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 ampere (c) 1 kilowatt-hour (kWh) (d) 1 watt

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