Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 247 · 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.True or false: to set the AC to 24 °C saves electricity. (a) True (b) False
2. 2.🌈 A resistor has the colour bands blue, grey, red. What is its value (in ohms)?
3. 3.💡 A blue LED uses 3 V and should get 20 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
4. 4.🔺 A 10 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
5. 5.🧮 Resistors of 470 Ω, 150 Ω, 150 Ω and 150 Ω are joined in series. What is the total resistance (in ohms)?
6. 6.🧮 A 2.2 V battery is joined to 3 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
7. 7.🧩 Which component smooths a wobbly supply? (a) resistor (b) capacitor (c) motor (d) buzzer
8. 8.Which of these is measured in ohms (Ω)? (a) the push of a cell (b) resistance (c) current (d) power
9. 9.🔺 A 1.5 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
10. 10.🧩 Which component senses how hot it is? (a) thermistor (b) diode (c) transistor (d) LDR
11. 11.True or false: the ammeter measures current. (a) True (b) False
12. 12.🔺 A current of 3 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
13. 13.What does a fuse do? (a) blows if current is high (b) stores a little charge (c) senses how hot it is (d) glows using little power
14. 14.🧾 Which lamp gives the same light for the least power? (a) an oil lamp (b) a candle (c) a filament bulb (d) an LED lamp
15. 15.🔺 A current of 10 mA flows when 3.3 V is joined across a resistor. What is its resistance (in ohms)?
16. 16.🌈 A resistor has the colour bands white, white, red. What is its value (in ohms)?
17. 17.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
18. 18.🔍 Which is the odd one out? (a) iron one shirt at a time (b) switch off empty rooms (c) use LED lamps (d) set the AC to 24 °C
19. 19.⚡ Power tells us … (a) energy used each second (b) the size of a cell (c) the colour of light (d) the length of a wire
20. 20.📏 Which unit measures current? (a) watt (W) (b) ohm (Ω) (c) volt (V) (d) ampere (A)
21. 21.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V ÷ I (c) P = V × I (d) P = V + I
22. 22.📏 How many kilowatts (kW) is 1750 W? =
23. 23.🔺 A current of 0.2 A flows when 1 V is joined across a resistor. What is its resistance (in ohms)?
24. 24.True or false: the voltmeter is joined in series. (a) False (b) True
25. 25.🌈 A resistor has the colour bands red, yellow, red. What is its value (in ohms)?
26. 26.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
27. 27.🌈 A resistor has the colour bands orange, black, brown. What is its value (in ohms)?
28. 28.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to an 8 V supply. What current flows (in mA)?
29. 29.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
30. 30.🧾 A 50 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
31. 31.🌈 A resistor has the colour bands red, black, orange. What is its value in kilo-ohms (kΩ)? =
32. 32.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) becomes zero (c) gets bigger (d) stays the same
33. 33.🔺 A current of 0.5 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
34. 34.🔍 Which is the odd one out? (a) leave fridge door open (b) iron one shirt at a time (c) use old filament bulbs (d) unplug idle chargers
35. 35.📏 In the water-pipe picture of a circuit, voltage is like … (a) the water pressure (b) the pipe colour (c) the tap handle (d) the water tank lid
36. 36.🔺 A current of 20 mA flows when 6.6 V is joined across a resistor. What is its resistance (in ohms)?
37. 37.🧩 Which component is a resistance knob? (a) resistor (b) thermistor (c) capacitor (d) potentiometer
38. 38.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 39 Ω resistor? (a) white-orange-black (b) orange-white-black (c) orange-white-brown (d) yellow-white-black
39. 39.🔺 An 18 V supply is joined across a 6 Ω resistor. What current flows (in amperes)? =
40. 40.🔺 A current of 2.5 A flows when 25 V is joined across a resistor. What is its resistance (in ohms)?

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