Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 960 · 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 25 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
2. 2.What does a motor do? (a) beeps for an alarm (b) senses how hot it is (c) makes things spin (d) limits the current
3. 3.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) gets bigger (c) becomes zero (d) gets smaller
4. 4.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) bigger (c) smaller (d) zero
5. 5.🔺 A 0.6 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
6. 6.🌈 Which band is read first on a resistor? (a) the gold band (b) the widest gap (c) any band (d) the one nearest an end
7. 7.📏 How many ohms (Ω) is 3.2 kΩ?
8. 8.True or false: the ammeter measures voltage. (a) False (b) True
9. 9.💡 An LED is joined to a 12 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) may burn out (b) lights up (c) does not light
10. 10.📏 Which unit measures voltage? (a) watt (W) (b) ohm (Ω) (c) ampere (A) (d) volt (V)
11. 11.💡 An LED is joined to a 9 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) does not light (c) lights up
12. 12.🔺 A 10 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
13. 13.True or false: a capacitor smooths a wobbly supply. (a) True (b) False
14. 14.🔍 Which is the odd one out? (a) iron one shirt at a time (b) use old filament bulbs (c) leave the TV on standby (d) set the AC to 24 °C
15. 15.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) True (b) False
16. 16.⚡ Power tells us … (a) the size of a cell (b) the colour of light (c) the length of a wire (d) energy used each second
17. 17.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
18. 18.True or false: a motor boosts a small signal. (a) False (b) True
19. 19.🧾 A 250 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
20. 20.📏 How many kilowatts (kW) is 300 W? =
21. 21.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 100 (b) 1024 (c) 1000 (d) 10
22. 22.🔺 A current of 2.5 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
23. 23.🌈 A resistor has the colour bands red, green, black. What is its value (in ohms)?
24. 24.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 93000 Ω resistor? (a) orange-white-orange (b) white-orange-orange (c) white-orange-red (d) white-orange-yellow
25. 25.🔺 A current of 0.25 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
26. 26.🔺 A current of 40 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
27. 27.🔺 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
28. 28.🧩 Which part changes electrical energy into sound? (a) a diode (b) a buzzer (c) a resistor (d) a capacitor
29. 29.🧩 Which component makes things spin? (a) fuse (b) potentiometer (c) motor (d) diode
30. 30.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
31. 31.🌈 A resistor has the colour bands brown, grey, red. What is its value (in ohms)?
32. 32.🔺 A current of 0.5 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
33. 33.🧩 Which component stores a little charge? (a) thermistor (b) capacitor (c) diode (d) potentiometer
34. 34.🔺 A current of 25 mA flows when 11.75 V is joined across a resistor. What is its resistance (in ohms)?
35. 35.🔺 A current of 40 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
36. 36.🧾 One “unit” on an electricity bill is … (a) 1 kilowatt-hour (kWh) (b) 1 watt (c) 1 ampere (d) 1 volt
37. 37.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 2.75 V supply. What current flows (in mA)?
38. 38.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 10 hours. How many watt-hours (Wh) are saved?
39. 39.🔺 A 12.5 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
40. 40.🧮 Resistors of 100 Ω, 33 Ω and 100 Ω are joined in series. What is the total resistance (in ohms)?

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