Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 242 · 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 4 A. What is its power (in watts)?
2. 2.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
3. 3.🧮 A 470 Ω resistor is joined in series with two equal 40 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
4. 4.🔺 A current of 1.5 A flows when 15 V is joined across a resistor. What is its resistance (in ohms)?
5. 5.🧮 A 13 V battery is joined to 10 Ω and 3 Ω resistors in series. What current flows (in amperes)? =
6. 6.🔺 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
7. 7.🧾 Which lamp gives the same light for the least power? (a) an LED lamp (b) an oil lamp (c) a filament bulb (d) a candle
8. 8.What does an LED do? (a) glows using little power (b) makes a beeping sound (c) smooths a wobbly supply (d) beeps for an alarm
9. 9.🧮 A 150 Ω resistor is joined in series with two equal 200 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
10. 10.🧮 A 0.6 V battery is joined to 2 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
11. 11.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 4 V supply. What current flows (in mA)?
12. 12.🔺 A current of 20 mA flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
13. 13.🧮 Two resistors in parallel give a total that is … (a) their sum (b) more than either one (c) always zero (d) less than either one
14. 14.🔺 A current of 2.5 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
15. 15.🔺 A 4 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
16. 16.🔺 A current of 0.1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
17. 17.⚡ A 0.6 W device works on 6 V. What current does it take (in amperes)? =
18. 18.🌈 Which band is read first on a resistor? (a) the gold band (b) any band (c) the one nearest an end (d) the widest gap
19. 19.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) smaller (c) stay the same (d) bigger
20. 20.True or false: the ammeter is joined across a part. (a) True (b) False
21. 21.🔺 A 10 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
22. 22.🔺 A current of 0.2 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
23. 23.🧮 Resistors of 470 Ω, 22 Ω, 33 Ω and 100 Ω are joined in series. What is the total resistance (in ohms)?
24. 24.🧩 Which component makes things spin? (a) fuse (b) motor (c) diode (d) capacitor
25. 25.🔺 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
26. 26.💡 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?
27. 27.⚡ Power tells us … (a) energy used each second (b) the size of a cell (c) the length of a wire (d) the colour of light
28. 28.Which of these saves electricity? (a) iron one shirt at a time (b) leave fridge door open (c) set the AC to 24 °C (d) run fans in empty rooms
29. 29.🧾 A 50 W appliance runs for 6 hours. How many units (kWh) of electricity does it use? =
30. 30.⚡ A device works on 12 V and takes 0.5 A. What is its power (in watts)? =
31. 31.True or false: energy used each second is measured in watts (W). (a) True (b) False
32. 32.⚡ A device works on 24 V and takes 0.25 A. What is its power (in watts)? =
33. 33.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = I ÷ V (c) P = V + I (d) P = V × I
34. 34.🔍 Which is the odd one out? (a) use old filament bulbs (b) leave the TV on standby (c) leave fridge door open (d) unplug idle chargers
35. 35.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 0 % (c) 25 % (d) 5 %
36. 36.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) gets smaller (c) gets bigger (d) becomes zero
37. 37.🌈 A resistor has the colour bands orange, yellow, black. What is its value (in ohms)?
38. 38.🔺 In the V-I-R triangle, how do we find R? (a) R = V ÷ I (b) R = I ÷ V (c) R = V + I (d) R = V × I
39. 39.Which of these saves electricity? (a) leave fridge door open (b) use daylight to read (c) use old filament bulbs (d) leave the TV on standby
40. 40.True or false: the ammeter measures current. (a) True (b) False

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