Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 826 · 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.🔺 A 10 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
2. 2.🔺 A current of 25 mA flows when 3.75 V is joined across a resistor. What is its resistance (in ohms)?
3. 3.🌈 Which band is read first on a resistor? (a) any band (b) the gold band (c) the widest gap (d) the one nearest an end
4. 4.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 3 hours. How many watt-hours (Wh) are saved?
5. 5.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) bigger (c) stay the same (d) zero
6. 6.🌈 A resistor has the colour bands white, brown, red. What is its value in kilo-ohms (kΩ)? =
7. 7.⚡ Power tells us … (a) energy used each second (b) the length of a wire (c) the size of a cell (d) the colour of light
8. 8.🔺 In the V-I-R triangle, how do we find I? (a) I = V + R (b) I = V ÷ R (c) I = R ÷ V (d) I = V × R
9. 9.🔺 A 2.5 V supply is joined across a 250 Ω resistor. What current flows (in milliamperes, mA)?
10. 10.🔺 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
11. 11.True or false: the ammeter is joined across a part. (a) False (b) True
12. 12.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
13. 13.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
14. 14.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 6.5 V supply. What current flows (in mA)?
15. 15.⚡ A device works on 9 V and takes 0.1 A. What is its power (in watts)? =
16. 16.💡 An LED is joined to a 3 V battery through a 470 Ω resistor; the leg next to the flat edge of its rim goes to the + side. What happens? (a) may burn out (b) lights up (c) does not light
17. 17.🌈 A resistor has the colour bands grey, red, brown. What is its value (in ohms)?
18. 18.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 3.5 V supply. What current flows (in mA)?
19. 19.🧾 Which lamp gives the same light for the least power? (a) an oil lamp (b) a candle (c) an LED lamp (d) a filament bulb
20. 20.🔺 A current of 1 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
21. 21.🧮 Four equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
22. 22.🧩 Which component makes a beeping sound? (a) transistor (b) potentiometer (c) thermistor (d) buzzer
23. 23.🧩 Which component has coloured bands? (a) resistor (b) fuse (c) buzzer (d) transistor
24. 24.🧩 Which component blows if current is high? (a) motor (b) potentiometer (c) resistor (d) fuse
25. 25.🔺 A current of 25 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
26. 26.⚡ A device works on 6 V and takes 3 A. What is its power (in watts)? =
27. 27.🌈 A resistor has the colour bands red, green, brown. What is its value (in ohms)?
28. 28.🔺 A current of 40 mA flows when 16 V is joined across a resistor. What is its resistance (in ohms)?
29. 29.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
30. 30.📏 Which unit measures the flow of charge? (a) watt (W) (b) ohm (Ω) (c) ampere (A) (d) volt (V)
31. 31.🧮 Resistors of 470 Ω, 10 Ω and 68 Ω are joined in series. What is the total resistance (in ohms)?
32. 32.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 5 % (c) 25 % (d) 0 %
33. 33.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
34. 34.🧩 Which part changes electrical energy into movement? (a) a motor (b) a resistor (c) a fuse (d) an LED
35. 35.True or false: the voltmeter is joined in series. (a) True (b) False
36. 36.📏 Which unit measures power? (a) watt (W) (b) ampere (A) (c) volt (V) (d) ohm (Ω)
37. 37.Which of these saves electricity? (a) iron one shirt at a time (b) unplug idle chargers (c) run fans in empty rooms (d) leave the TV on standby
38. 38.🔺 A 5 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
39. 39.🧮 Five equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
40. 40.🔺 A current of 0.2 A flows when 2.4 V is joined across a resistor. What is its resistance (in ohms)?

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