Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 114 · 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 home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
2. 2.🧮 A 330 Ω resistor is joined in series with two equal 220 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
3. 3.🧮 A 10 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)?
4. 4.🔺 A current of 50 mA flows when 23.5 V is joined across a resistor. What is its resistance (in ohms)?
5. 5.🔺 A 20 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
6. 6.What does a thermistor do? (a) senses how hot it is (b) stores a little charge (c) makes a beeping sound (d) lets current go one way
7. 7.🌈 A resistor has the colour bands red, violet, red. What is its value (in ohms)?
8. 8.True or false: on an LED, the shorter leg is the cathode (−). (a) False (b) True
9. 9.True or false: an LDR limits the current. (a) False (b) True
10. 10.Which of these saves electricity? (a) use old filament bulbs (b) leave the TV on standby (c) run fans in empty rooms (d) close the fridge quickly
11. 11.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 2 hours. How many watt-hours (Wh) are saved?
12. 12.🧮 Three equal 75 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
13. 13.📏 How many ohms (Ω) is 2 kΩ?
14. 14.🧮 Two equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
15. 15.🔺 A 0.5 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
16. 16.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 1000 (b) 10 (c) 100 (d) 1024
17. 17.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 8300 Ω resistor? (a) orange-grey-red (b) grey-orange-red (c) grey-orange-orange (d) grey-orange-brown
18. 18.True or false: a fuse blows if current is high. (a) True (b) False
19. 19.📏 Which unit measures voltage? (a) watt (W) (b) volt (V) (c) ohm (Ω) (d) ampere (A)
20. 20.🌈 A resistor has the colour bands yellow, blue, yellow. What is its value in kilo-ohms (kΩ)? =
21. 21.🧮 Resistors of 330 Ω, 330 Ω, 330 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
22. 22.🔺 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
23. 23.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) zero (c) smaller (d) bigger
24. 24.🧩 Which part changes electrical energy into sound? (a) a buzzer (b) a resistor (c) a capacitor (d) a diode
25. 25.🧮 A 16 V battery is joined to 4 Ω and 12 Ω resistors in series. What current flows (in amperes)? =
26. 26.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
27. 27.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) becomes zero (c) stays the same (d) gets bigger
28. 28.🧩 Which component has coloured bands? (a) diode (b) capacitor (c) thermistor (d) resistor
29. 29.📏 How many kilo-ohms (kΩ) is 6400 Ω? =
30. 30.True or false: a capacitor stores a little charge. (a) True (b) False
31. 31.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
32. 32.🧾 A 2000 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
33. 33.🧮 A 2.8 V battery is joined to 4 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
34. 34.🧩 Which part changes electrical energy into movement? (a) a fuse (b) a resistor (c) an LED (d) a motor
35. 35.🔺 A current of 0.1 A flows when 0.6 V is joined across a resistor. What is its resistance (in ohms)?
36. 36.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = I + R (c) V = R ÷ I (d) V = I × R
37. 37.🌈 A gold fourth band on a resistor means the value may be off by … (a) 0 % (b) 5 % (c) 25 % (d) 50 %
38. 38.🌈 In the resistor colour code, which number does black stand for?
39. 39.⚡ A device works on 1.5 V and takes 0.5 A. What is its power (in watts)? =
40. 40.Which of these wastes electricity? (a) close the fridge quickly (b) set the AC to 24 °C (c) unplug idle chargers (d) run fans in empty rooms

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