Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 352 · 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.💡 Does it save or waste electricity to set the AC to 24 °C? (a) wastes electricity (b) saves electricity
2. 2.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V + I (c) P = V ÷ I (d) P = V × I
3. 3.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
4. 4.True or false: on an LED, the leg by the flat edge is the anode (+). (a) True (b) False
5. 5.🔺 A current of 0.5 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
6. 6.🔺 A 25 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
7. 7.🧮 A 20 Ω resistor is joined in series with two equal 330 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
8. 8.True or false: resistance is measured in ohms (Ω). (a) False (b) True
9. 9.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
10. 10.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
11. 11.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 2 hours. How many watt-hours (Wh) are saved?
12. 12.True or false: to run fans in empty rooms saves electricity. (a) False (b) True
13. 13.🧾 A 250 W appliance runs for 6 hours. How many units (kWh) of electricity does it use? =
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) lights up (c) may burn out
15. 15.🔺 A current of 25 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
16. 16.🔺 In the V-I-R triangle, how do we find V? (a) V = R ÷ I (b) V = I × R (c) V = I ÷ R (d) V = I + R
17. 17.Which of these is measured in ohms (Ω)? (a) power (b) voltage (c) resistance (d) current
18. 18.⚡ A 0.15 W device works on 1.5 V. What current does it take (in amperes)? =
19. 19.📏 Which unit measures the push of a cell? (a) volt (V) (b) ampere (A) (c) watt (W) (d) ohm (Ω)
20. 20.🔺 A current of 20 mA flows when 10 V is joined across a resistor. What is its resistance (in ohms)?
21. 21.True or false: the ammeter is joined in series. (a) False (b) True
22. 22.🔍 Which is the odd one out? (a) unplug idle chargers (b) use old filament bulbs (c) leave fridge door open (d) run fans in empty rooms
23. 23.⚡ Power tells us … (a) the colour of light (b) the length of a wire (c) the size of a cell (d) energy used each second
24. 24.🧩 Which component senses how bright it is? (a) LDR (b) thermistor (c) buzzer (d) diode
25. 25.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
26. 26.📏 Voltmeter or ammeter: which one measures current? (a) voltmeter (b) ammeter
27. 27.💡 A red LED uses 2 V and should get 25 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
28. 28.🔺 A 1.5 V supply is joined across a 6 Ω resistor. What current flows (in amperes)? =
29. 29.⚡ A device works on 12 V and takes 0.2 A. What is its power (in watts)? =
30. 30.📏 How many milliamperes (mA) is 1.02 A?
31. 31.🌈 A resistor has the colour bands green, blue, yellow. What is its value in kilo-ohms (kΩ)? =
32. 32.🔺 A current of 10 mA flows when 2.5 V is joined across a resistor. What is its resistance (in ohms)?
33. 33.🧩 Which part changes electrical energy into movement? (a) a fuse (b) a motor (c) a resistor (d) an LED
34. 34.What does a resistor do? (a) lets current go one way (b) stores a little charge (c) has coloured bands (d) makes things spin
35. 35.True or false: a resistor has coloured bands. (a) True (b) False
36. 36.📏 Which unit measures power? (a) volt (V) (b) ohm (Ω) (c) watt (W) (d) ampere (A)
37. 37.🌈 A resistor has the colour bands brown, grey, brown. What is its value (in ohms)?
38. 38.True or false: the flow of charge is measured in volts (V). (a) False (b) True
39. 39.🔺 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
40. 40.True or false: to use daylight to read wastes electricity. (a) True (b) False

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