Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 99 · 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.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
2. 2.⚡ Which formula gives electric power? (a) P = V × I (b) P = I ÷ V (c) P = V + I (d) P = V ÷ I
3. 3.🔺 A current of 25 mA flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
4. 4.🔺 A current of 10 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
5. 5.🧮 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
6. 6.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
7. 7.🧾 A 200 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
8. 8.True or false: on an LED, the shorter leg is the anode (+). (a) False (b) True
9. 9.⚡ A device works on 5 V and takes 2 A. What is its power (in watts)? =
10. 10.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
11. 11.🌈 Which band is read first on a resistor? (a) the widest gap (b) the one nearest an end (c) the gold band (d) any band
12. 12.🔺 A current of 20 mA flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
13. 13.🔺 A current of 10 mA flows when 2.5 V is joined across a resistor. What is its resistance (in ohms)?
14. 14.⚡ A 6 W device works on 3 V. What current does it take (in amperes)? =
15. 15.🔺 In the V-I-R triangle, how do we find I? (a) I = R ÷ V (b) I = V + R (c) I = V × R (d) I = V ÷ R
16. 16.📏 How many milliamperes (mA) is 0.03 A?
17. 17.🌈 A resistor has the colour bands red, grey, orange. What is its value in kilo-ohms (kΩ)? =
18. 18.🔺 A current of 3 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
19. 19.True or false: an LDR turns a fan or wheels. (a) True (b) False
20. 20.🔍 Which is the odd one out? (a) switch off empty rooms (b) use old filament bulbs (c) set the AC to 24 °C (d) use daylight to read
21. 21.📏 In the water-pipe picture of a circuit, voltage is like … (a) the pipe colour (b) the tap handle (c) the water tank lid (d) the water pressure
22. 22.Which of these is measured in amperes (A)? (a) the push of a cell (b) voltage (c) current (d) resistance
23. 23.🔺 A current of 0.25 A flows when 0.75 V is joined across a resistor. What is its resistance (in ohms)?
24. 24.🔺 A current of 10 mA flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
25. 25.⚡ Power tells us … (a) the size of a cell (b) the colour of light (c) the length of a wire (d) energy used each second
26. 26.True or false: to use old filament bulbs saves electricity. (a) True (b) False
27. 27.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
28. 28.💡 What happens if an LED is put in backwards? (a) it makes a sound (b) it does not light (c) it lights brighter (d) it changes colour
29. 29.💡 What does LED stand for? (a) large electric dial (b) light-emitting diode (c) light energy dial (d) low energy device
30. 30.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 5 V supply. What current flows (in mA)?
31. 31.⚡ A device works on 1.5 V and takes 2 A. What is its power (in watts)? =
32. 32.🧮 Four equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
33. 33.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
34. 34.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to make it brighter (c) to limit the current (d) to store charge
35. 35.📏 How many ohms (Ω) is 8.4 kΩ?
36. 36.True or false: on an LED, the longer leg is the anode (+). (a) False (b) True
37. 37.📏 Which unit measures the flow of charge? (a) ohm (Ω) (b) watt (W) (c) volt (V) (d) ampere (A)
38. 38.🌈 A resistor has the colour bands red, grey, brown. What is its value (in ohms)?
39. 39.True or false: on an LED, the leg by the flat edge is the anode (+). (a) True (b) False
40. 40.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 6 V supply. What current flows (in mA)?

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