Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 185 · 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.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V + I (c) P = V × I (d) P = V ÷ I
2. 2.🌈 A gold fourth band on a resistor means the value may be off by … (a) 0 % (b) 5 % (c) 50 % (d) 25 %
3. 3.Which of these is measured in amperes (A)? (a) the push of a cell (b) how much a part resists (c) resistance (d) current
4. 4.📏 How many kilo-ohms (kΩ) is 8900 Ω? =
5. 5.🌈 In the resistor colour code, which number does yellow stand for?
6. 6.⚡ A device works on 6 V and takes 2 A. What is its power (in watts)? =
7. 7.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) False (b) True
8. 8.🧮 Resistors of 470 Ω, 68 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
9. 9.🧾 One “unit” on an electricity bill is … (a) 1 watt (b) 1 ampere (c) 1 kilowatt-hour (kWh) (d) 1 volt
10. 10.🧮 A 2.25 V battery is joined to 3 Ω and 6 Ω resistors in series. What current flows (in amperes)? =
11. 11.True or false: the voltmeter measures current. (a) True (b) False
12. 12.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
13. 13.🔺 A current of 2.5 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
14. 14.True or false: to use old filament bulbs wastes electricity. (a) False (b) True
15. 15.🔺 A 1.2 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
16. 16.🧮 Two resistors in parallel give a total that is … (a) always zero (b) their sum (c) less than either one (d) more than either one
17. 17.True or false: the voltmeter is joined in series. (a) False (b) True
18. 18.📏 In the water-pipe picture of a circuit, voltage is like … (a) the pipe colour (b) the water pressure (c) the water tank lid (d) the tap handle
19. 19.🔍 Which is the odd one out? (a) use old filament bulbs (b) unplug idle chargers (c) set the AC to 24 °C (d) use LED lamps
20. 20.🧩 Which component is a resistance knob? (a) LDR (b) buzzer (c) potentiometer (d) motor
21. 21.🔺 A current of 0.1 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
22. 22.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = V + I (c) R = I ÷ V (d) R = V ÷ I
23. 23.🔍 Which is the odd one out? (a) leave fridge door open (b) iron one shirt at a time (c) leave the TV on standby (d) use daylight to read
24. 24.🔺 In the V-I-R triangle, how do we find I? (a) I = V × R (b) I = V + R (c) I = V ÷ R (d) I = R ÷ V
25. 25.True or false: a capacitor limits the current. (a) True (b) False
26. 26.🔺 A current of 50 mA flows when 12.5 V is joined across a resistor. What is its resistance (in ohms)?
27. 27.📏 Which unit measures energy used each second? (a) ampere (A) (b) watt (W) (c) volt (V) (d) ohm (Ω)
28. 28.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) stays the same (c) gets bigger (d) becomes zero
29. 29.🔺 A 2.5 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
30. 30.📏 Voltmeter or ammeter: which one measures current? (a) ammeter (b) voltmeter
31. 31.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 190 Ω resistor? (a) brown-white-brown (b) white-brown-brown (c) brown-white-black (d) brown-white-red
32. 32.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 380 Ω resistor? (a) orange-grey-brown (b) grey-orange-brown (c) orange-grey-black (d) orange-grey-red
33. 33.💡 Does it save or waste electricity to leave fridge door open? (a) saves electricity (b) wastes electricity
34. 34.🔺 A current of 10 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
35. 35.📏 How many kilowatts (kW) is 2250 W? =
36. 36.🔺 An 11.75 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
37. 37.🧩 Which part changes electrical energy into sound? (a) a capacitor (b) a buzzer (c) a resistor (d) a diode
38. 38.What does an LDR do? (a) glows using little power (b) lets current go one way (c) senses how bright it is (d) beeps for an alarm
39. 39.🧩 Which component has coloured bands? (a) capacitor (b) LDR (c) resistor (d) transistor
40. 40.📏 Which unit measures the push of a cell? (a) ohm (Ω) (b) volt (V) (c) watt (W) (d) ampere (A)

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