Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 475 · 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.🌈 In the resistor colour code, which number does grey stand for?
2. 2.⚡ A 12 W device works on 12 V. What current does it take (in amperes)? =
3. 3.⚡ A 12 W device works on 24 V. What current does it take (in amperes)? =
4. 4.🧩 Which component limits the current? (a) motor (b) diode (c) resistor (d) potentiometer
5. 5.🔺 In the V-I-R triangle, how do we find V? (a) V = I + R (b) V = I ÷ R (c) V = I × R (d) V = R ÷ I
6. 6.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) stays the same (c) becomes zero (d) gets smaller
7. 7.🔺 A 3 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
8. 8.🔺 A 7.5 V supply is joined across a 150 Ω resistor. What current flows (in milliamperes, mA)?
9. 9.💡 Does it save or waste electricity to set the AC to 24 °C? (a) saves electricity (b) wastes electricity
10. 10.True or false: a buzzer makes a beeping sound. (a) True (b) False
11. 11.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
12. 12.⚡ A device works on 1.5 V and takes 0.1 A. What is its power (in watts)? =
13. 13.💡 What happens if an LED is put in backwards? (a) it changes colour (b) it makes a sound (c) it lights brighter (d) it does not light
14. 14.📏 How many milliamperes (mA) make 1 ampere? (a) 1000 (b) 10 (c) 60 (d) 100
15. 15.🌈 A resistor has the colour bands violet, brown, brown. What is its value (in ohms)?
16. 16.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 8 hours. How many watt-hours (Wh) are saved?
17. 17.🔺 A current of 0.1 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
18. 18.🧾 A 200 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
19. 19.True or false: on an LED, the round-side leg is the cathode (−). (a) False (b) True
20. 20.🧩 Which component smooths a wobbly supply? (a) LED (b) capacitor (c) fuse (d) buzzer
21. 21.Which of these is measured in amperes (A)? (a) current (b) the push of a cell (c) power (d) energy used each second
22. 22.🔺 A current of 20 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
23. 23.True or false: the push of a cell is measured in volts (V). (a) False (b) True
24. 24.🌈 In the resistor colour code, which number does green stand for?
25. 25.🧮 Three equal 30 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
26. 26.🧮 A 470 Ω resistor is joined in series with two equal 10 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
27. 27.🧮 A 1.3 V battery is joined to 10 Ω and 3 Ω resistors in series. What current flows (in amperes)? =
28. 28.🔺 A current of 20 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
29. 29.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
30. 30.🧮 Five equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
31. 31.📏 How many kilo-ohms (kΩ) is 100 Ω? =
32. 32.🔺 A current of 20 mA flows when 6.6 V is joined across a resistor. What is its resistance (in ohms)?
33. 33.🔺 A current of 1.5 A flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
34. 34.🧮 A 0.9 V battery is joined to 5 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
35. 35.🔍 Which is the odd one out? (a) use LED lamps (b) use old filament bulbs (c) close the fridge quickly (d) unplug idle chargers
36. 36.🌈 Which band is read first on a resistor? (a) the gold band (b) the one nearest an end (c) any band (d) the widest gap
37. 37.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
38. 38.⚡ A 0.6 W device works on 6 V. What current does it take (in amperes)? =
39. 39.📏 How many amperes (A) is 1790 mA? =
40. 40.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)

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