Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 172 · 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 1.4 V battery is joined to 4 Ω and 3 Ω resistors in series. What current flows (in amperes)? =
2. 2.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
3. 3.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 25 % (c) 5 % (d) 0 %
4. 4.🧮 Two equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
5. 5.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to store charge (c) to limit the current (d) to change its colour
6. 6.🌈 Which band is read first on a resistor? (a) the one nearest an end (b) the widest gap (c) the gold band (d) any band
7. 7.💡 A blue LED uses 3 V and should get 10 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
8. 8.True or false: a capacitor senses how hot it is. (a) True (b) False
9. 9.⚡ Power tells us … (a) the length of a wire (b) the size of a cell (c) the colour of light (d) energy used each second
10. 10.🔺 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
11. 11.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) zero (c) stay the same (d) bigger
12. 12.🌈 In the resistor colour code, which number does orange stand for?
13. 13.🌈 A resistor has the colour bands blue, grey, brown. What is its value (in ohms)?
14. 14.🧩 Which component makes a beeping sound? (a) resistor (b) buzzer (c) fuse (d) diode
15. 15.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
16. 16.🔺 A current of 0.25 A flows when 0.75 V is joined across a resistor. What is its resistance (in ohms)?
17. 17.🔺 A current of 50 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
18. 18.🧩 Which part changes electrical energy into sound? (a) a capacitor (b) a buzzer (c) a diode (d) a resistor
19. 19.🌈 A resistor has the colour bands green, yellow, brown. What is its value (in ohms)?
20. 20.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 610 Ω resistor? (a) blue-brown-black (b) blue-brown-brown (c) brown-blue-brown (d) blue-brown-red
21. 21.Which of these saves electricity? (a) iron one shirt at a time (b) use old filament bulbs (c) set the AC to 24 °C (d) run fans in empty rooms
22. 22.🧮 Resistors of 470 Ω, 33 Ω and 220 Ω are joined in series. What is the total resistance (in ohms)?
23. 23.🧮 A 2.6 V battery is joined to 8 Ω and 5 Ω resistors in series. What current flows (in amperes)? =
24. 24.💡 An LED is joined to a 5 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) lights up (b) does not light (c) may burn out
25. 25.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
26. 26.📏 How many ohms (Ω) is 5.3 kΩ?
27. 27.🧩 Which component turns a fan or wheels? (a) motor (b) LDR (c) diode (d) fuse
28. 28.🧮 Three equal 75 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
29. 29.📏 How many kilo-ohms (kΩ) is 4300 Ω? =
30. 30.🔺 A current of 2 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
31. 31.🔺 A current of 25 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
32. 32.⚡ A 6 W device works on 12 V. What current does it take (in amperes)? =
33. 33.💡 What happens if an LED is put in backwards? (a) it does not light (b) it lights brighter (c) it makes a sound (d) it changes colour
34. 34.🔺 A current of 0.1 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
35. 35.💡 Does it save or waste electricity to leave fridge door open? (a) saves electricity (b) wastes electricity
36. 36.🔺 A current of 40 mA flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
37. 37.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
38. 38.🔺 A current of 40 mA flows when 13.2 V is joined across a resistor. What is its resistance (in ohms)?
39. 39.🧮 Resistors of 20 Ω, 20 Ω, 10 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
40. 40.🔺 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

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