Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 810 · 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.True or false: current is measured in amperes (A). (a) True (b) False
2. 2.📏 How many milliamperes (mA) is 1.3 A?
3. 3.📏 How many amperes (A) is 290 mA? =
4. 4.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 590 Ω resistor? (a) green-white-red (b) green-white-black (c) green-white-brown (d) white-green-brown
5. 5.True or false: on an LED, the round-side leg is the cathode (−). (a) False (b) True
6. 6.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) gets smaller (c) gets bigger (d) stays the same
7. 7.🧮 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
8. 8.⚡ A device works on 3 V and takes 0.5 A. What is its power (in watts)? =
9. 9.🔺 A current of 50 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
10. 10.💡 An LED is joined to a 5 V battery through a 220 Ω resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) may burn out (b) does not light (c) lights up
11. 11.🧩 Which component has coloured bands? (a) resistor (b) capacitor (c) thermistor (d) LDR
12. 12.What does an LED do? (a) senses how hot it is (b) is a resistance knob (c) glows using little power (d) beeps for an alarm
13. 13.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
14. 14.💡 An LED is joined to a 5 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) does not light (b) may burn out (c) lights up
15. 15.🔺 A current of 0.5 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
16. 16.What does an LDR do? (a) limits the current (b) is a resistance knob (c) turns a fan or wheels (d) senses how bright it is
17. 17.💡 Does it save or waste electricity to use daylight to read? (a) wastes electricity (b) saves electricity
18. 18.📏 How many milliamperes (mA) is 1.63 A?
19. 19.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
20. 20.⚡ Power tells us … (a) the length of a wire (b) energy used each second (c) the size of a cell (d) the colour of light
21. 21.⚡ A 15 W device works on 5 V. What current does it take (in amperes)? =
22. 22.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
23. 23.🌈 Which band is read first on a resistor? (a) any band (b) the one nearest an end (c) the widest gap (d) the gold band
24. 24.🧾 One “unit” on an electricity bill is … (a) 1 ampere (b) 1 volt (c) 1 watt (d) 1 kilowatt-hour (kWh)
25. 25.Which of these saves electricity? (a) iron one shirt at a time (b) use LED lamps (c) use old filament bulbs (d) leave fridge door open
26. 26.🌈 A resistor has the colour bands red, blue, red. What is its value in kilo-ohms (kΩ)? =
27. 27.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
28. 28.📏 How many amperes (A) is 100 mA? =
29. 29.🧮 Resistors of 50 Ω, 22 Ω, 10 Ω and 22 Ω are joined in series. What is the total resistance (in ohms)?
30. 30.🌈 A resistor has the colour bands green, yellow, black. What is its value (in ohms)?
31. 31.True or false: on an LED, the longer leg is the anode (+). (a) False (b) True
32. 32.💡 Does it save or waste electricity to run fans in empty rooms? (a) saves electricity (b) wastes electricity
33. 33.🔺 A current of 2.5 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
34. 34.📏 Voltmeter or ammeter: which one measures current? (a) ammeter (b) voltmeter
35. 35.💡 What does LED stand for? (a) large electric dial (b) light energy dial (c) light-emitting diode (d) low energy device
36. 36.💡 An LED is joined to a 9 V battery with no 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
37. 37.📏 Which unit measures the push of a cell? (a) ohm (Ω) (b) watt (W) (c) volt (V) (d) ampere (A)
38. 38.💡 Why does an LED need a resistor in series? (a) to store charge (b) to limit the current (c) to make it brighter (d) to change its colour
39. 39.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
40. 40.🌈 In the resistor colour code, which number does green stand for?

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