Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 784 · 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: a transistor boosts a small signal. (a) False (b) True
2. 2.⚡ A device works on 3 V and takes 1 A. What is its power (in watts)? =
3. 3.🌈 A gold fourth band on a resistor means the value may be off by … (a) 0 % (b) 5 % (c) 25 % (d) 50 %
4. 4.🔺 A current of 0.1 A flows when 0.8 V is joined across a resistor. What is its resistance (in ohms)?
5. 5.⚡ A device works on 9 V and takes 1.5 A. What is its power (in watts)? =
6. 6.📏 How many milliamperes (mA) is 0.78 A?
7. 7.🌈 A resistor has the colour bands white, yellow, orange. What is its value in kilo-ohms (kΩ)? =
8. 8.⚡ Which formula gives electric power? (a) P = V × I (b) P = V ÷ I (c) P = V + I (d) P = I ÷ V
9. 9.🔍 Which is the odd one out? (a) iron one shirt at a time (b) run fans in empty rooms (c) leave the TV on standby (d) close the fridge quickly
10. 10.💡 Does it save or waste electricity to set the AC to 24 °C? (a) wastes electricity (b) saves electricity
11. 11.True or false: to leave the TV on standby saves electricity. (a) False (b) True
12. 12.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
13. 13.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to limit the current (c) to store charge (d) to make it brighter
14. 14.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
15. 15.🔺 A current of 50 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
16. 16.🧮 An 8 V battery is joined to 4 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
17. 17.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
18. 18.💡 A red LED uses 2 V and should get 10 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
19. 19.⚡ Power tells us … (a) the size of a cell (b) energy used each second (c) the length of a wire (d) the colour of light
20. 20.🔺 A 20 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
21. 21.📏 Which unit measures the flow of charge? (a) watt (W) (b) volt (V) (c) ampere (A) (d) ohm (Ω)
22. 22.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
23. 23.True or false: a buzzer limits the current. (a) False (b) True
24. 24.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
25. 25.🧮 Resistors of 22 Ω, 10 Ω and 330 Ω are joined in series. What is the total resistance (in ohms)?
26. 26.🔺 A current of 10 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
27. 27.🧩 Which component limits the current? (a) capacitor (b) diode (c) potentiometer (d) resistor
28. 28.Which of these wastes electricity? (a) unplug idle chargers (b) switch off empty rooms (c) leave fridge door open (d) use LED lamps
29. 29.🌈 A resistor has the colour bands brown, green, brown. What is its value (in ohms)?
30. 30.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
31. 31.Which of these wastes electricity? (a) use daylight to read (b) switch off empty rooms (c) use LED lamps (d) iron one shirt at a time
32. 32.🔺 A 25 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
33. 33.🔺 In the V-I-R triangle, how do we find I? (a) I = V ÷ R (b) I = V + R (c) I = V × R (d) I = R ÷ V
34. 34.Which of these is measured in volts (V)? (a) the push of a cell (b) energy used each second (c) how much a part resists (d) power
35. 35.🧮 A 33 Ω resistor is joined in series with two equal 1000 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
36. 36.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
37. 37.🔺 A current of 20 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
38. 38.🧩 Which component turns a fan or wheels? (a) capacitor (b) LDR (c) motor (d) fuse
39. 39.🌈 Which band is read first on a resistor? (a) the gold band (b) the widest gap (c) any band (d) the one nearest an end
40. 40.⚡ A device works on 24 V and takes 0.1 A. What is its power (in watts)? =

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