Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 726 · 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.🧮 Resistors of 220 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
2. 2.🧮 Two equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
3. 3.🌈 A resistor has the colour bands violet, violet, red. What is its value in kilo-ohms (kΩ)? =
4. 4.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 89000 Ω resistor? (a) grey-white-orange (b) grey-white-red (c) white-grey-orange (d) grey-white-yellow
5. 5.True or false: a resistor has coloured bands. (a) False (b) True
6. 6.Which of these saves electricity? (a) leave fridge door open (b) use old filament bulbs (c) leave the TV on standby (d) use LED lamps
7. 7.True or false: to set the AC to 24 °C wastes electricity. (a) False (b) True
8. 8.🔺 A current of 3 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
9. 9.📏 Which unit measures power? (a) volt (V) (b) ohm (Ω) (c) watt (W) (d) ampere (A)
10. 10.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V + I (c) P = I ÷ V (d) P = V × I
11. 11.🌈 A resistor has the colour bands red, red, red. What is its value in kilo-ohms (kΩ)? =
12. 12.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
13. 13.🧮 A 150 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)?
14. 14.💡 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?
15. 15.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 4200 Ω resistor? (a) yellow-red-red (b) red-yellow-red (c) yellow-red-orange (d) yellow-red-brown
16. 16.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
17. 17.📏 How many kilo-ohms (kΩ) is 5100 Ω? =
18. 18.🔺 A current of 50 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
19. 19.🔺 A current of 25 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
20. 20.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
21. 21.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 5 % (c) 50 % (d) 0 %
22. 22.📏 How many ohms (Ω) is 8.4 kΩ?
23. 23.🧾 A 50 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =
24. 24.🔺 A current of 10 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
25. 25.🔺 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
26. 26.🌈 Which band is read first on a resistor? (a) the one nearest an end (b) the widest gap (c) the gold band (d) any band
27. 27.🧾 A 2000 W appliance runs for 10 hours. How many units (kWh) of electricity does it use? =
28. 28.🧮 Resistors of 47 Ω and 150 Ω are joined in series. What is the total resistance (in ohms)?
29. 29.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 10 (b) 100 (c) 1024 (d) 1000
30. 30.🧩 Which component lets current go one way? (a) LED (b) diode (c) motor (d) capacitor
31. 31.🧩 Which component senses how hot it is? (a) LED (b) potentiometer (c) thermistor (d) fuse
32. 32.🧮 Two resistors in parallel give a total that is … (a) less than either one (b) more than either one (c) their sum (d) always zero
33. 33.Which of these wastes electricity? (a) switch off empty rooms (b) unplug idle chargers (c) leave fridge door open (d) use LED lamps
34. 34.💡 What does LED stand for? (a) light-emitting diode (b) large electric dial (c) low energy device (d) light energy dial
35. 35.True or false: the voltmeter is joined across a part. (a) False (b) True
36. 36.🔺 A 7.5 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
37. 37.True or false: power is measured in watts (W). (a) False (b) True
38. 38.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
39. 39.🌈 A resistor has the colour bands red, brown, orange. What is its value (in ohms)?
40. 40.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to limit the current (c) to make it brighter (d) to store charge

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