Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 300 · 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 current of 1.5 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
2. 2.🔺 A current of 0.25 A flows when 1.25 V is joined across a resistor. What is its resistance (in ohms)?
3. 3.What does a thermistor do? (a) has coloured bands (b) boosts a small signal (c) senses how hot it is (d) blows if current is high
4. 4.Which of these is measured in ohms (Ω)? (a) voltage (b) power (c) how much a part resists (d) the push of a cell
5. 5.🧾 A 1000 W appliance runs for 8 hours. How many units (kWh) of electricity does it use? =
6. 6.🧩 Which component has coloured bands? (a) capacitor (b) buzzer (c) resistor (d) diode
7. 7.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) always zero (c) their sum (d) less than either one
8. 8.🧮 A 22 Ω resistor is joined in series with two equal 20 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
9. 9.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = R ÷ I (c) V = I + R (d) V = I × R
10. 10.🧮 Resistors of 47 Ω, 150 Ω and 10 Ω are joined in series. What is the total resistance (in ohms)?
11. 11.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) gets smaller (c) becomes zero (d) gets bigger
12. 12.True or false: current is measured in volts (V). (a) True (b) False
13. 13.🧮 Resistors of 22 Ω, 47 Ω, 100 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
14. 14.🌈 A resistor has the colour bands brown, green, orange. What is its value in kilo-ohms (kΩ)? =
15. 15.⚡ A device works on 3 V and takes 0.25 A. What is its power (in watts)? =
16. 16.🔺 A current of 0.1 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
17. 17.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
18. 18.🌈 In the resistor colour code, which number does red stand for?
19. 19.🔺 A 6 V supply is joined across a 150 Ω resistor. What current flows (in milliamperes, mA)?
20. 20.🔺 In the V-I-R triangle, how do we find R? (a) R = V + I (b) R = V ÷ I (c) R = V × I (d) R = I ÷ V
21. 21.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 190 Ω resistor? (a) brown-white-red (b) white-brown-brown (c) brown-white-brown (d) brown-white-black
22. 22.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
23. 23.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it makes a sound (c) it changes colour (d) it does not light
24. 24.True or false: an LDR senses how bright it is. (a) True (b) False
25. 25.True or false: resistance is measured in ohms (Ω). (a) False (b) True
26. 26.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) zero (c) stay the same (d) bigger
27. 27.🌈 A resistor has the colour bands yellow, green, brown. What is its value (in ohms)?
28. 28.🔺 A 30 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
29. 29.📏 How many ohms (Ω) is 1.8 kΩ?
30. 30.🔺 A 3 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
31. 31.🧩 Which component blows if current is high? (a) motor (b) buzzer (c) fuse (d) capacitor
32. 32.🧮 Two equal 330 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
33. 33.⚡ Power tells us … (a) the length of a wire (b) the size of a cell (c) energy used each second (d) the colour of light
34. 34.🔺 In the V-I-R triangle, how do we find I? (a) I = V × R (b) I = R ÷ V (c) I = V ÷ R (d) I = V + R
35. 35.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
36. 36.Which of these saves electricity? (a) use old filament bulbs (b) leave fridge door open (c) leave the TV on standby (d) use LED lamps
37. 37.🧩 Which component smooths a wobbly supply? (a) capacitor (b) buzzer (c) motor (d) resistor
38. 38.🧮 Resistors of 68 Ω and 50 Ω are joined in series. What is the total resistance (in ohms)?
39. 39.📏 Which unit measures how much a part resists? (a) watt (W) (b) volt (V) (c) ampere (A) (d) ohm (Ω)
40. 40.🔺 A current of 20 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =

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