Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 555 · 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 of these wastes electricity? (a) switch off empty rooms (b) leave the TV on standby (c) use daylight to read (d) use LED lamps
2. 2.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
3. 3.📏 Which unit measures how much a part resists? (a) watt (W) (b) volt (V) (c) ampere (A) (d) ohm (Ω)
4. 4.🧩 Which component makes a beeping sound? (a) thermistor (b) resistor (c) potentiometer (d) buzzer
5. 5.📏 How many kilowatts (kW) is 2150 W? =
6. 6.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
7. 7.🔺 A 12.5 V supply is joined across a 250 Ω resistor. What current flows (in milliamperes, mA)?
8. 8.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
9. 9.What does an LED do? (a) lets current go one way (b) makes a beeping sound (c) glows using little power (d) stores a little charge
10. 10.⚡ Power tells us … (a) the colour of light (b) the length of a wire (c) the size of a cell (d) energy used each second
11. 11.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
12. 12.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 1000 (b) 10 (c) 1024 (d) 100
13. 13.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) gets smaller (c) gets bigger (d) stays the same
14. 14.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) less than either one (c) always zero (d) their sum
15. 15.⚡ A 2.4 W device works on 24 V. What current does it take (in amperes)? =
16. 16.🧮 A 2.5 V battery is joined to 2 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
17. 17.🔺 A current of 25 mA flows when 6.25 V is joined across a resistor. What is its resistance (in ohms)?
18. 18.🔍 Which is the odd one out? (a) leave the TV on standby (b) close the fridge quickly (c) set the AC to 24 °C (d) use daylight to read
19. 19.📏 How many kilo-ohms (kΩ) is 7600 Ω? =
20. 20.🧮 Resistors of 20 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
21. 21.🔺 A current of 40 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
22. 22.True or false: the ammeter is joined across a part. (a) True (b) False
23. 23.Which of these saves electricity? (a) set the AC to 24 °C (b) leave fridge door open (c) leave the TV on standby (d) run fans in empty rooms
24. 24.🔺 A 2.5 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
25. 25.🧩 Which component glows using little power? (a) LDR (b) potentiometer (c) capacitor (d) LED
26. 26.🔺 A 1 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
27. 27.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) zero (c) bigger (d) smaller
28. 28.🔺 A 10 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
29. 29.🧩 Which component senses how hot it is? (a) diode (b) motor (c) thermistor (d) buzzer
30. 30.🔺 A current of 10 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
31. 31.💡 What does LED stand for? (a) light energy dial (b) low energy device (c) large electric dial (d) light-emitting diode
32. 32.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
33. 33.🧩 Which part changes electrical energy into movement? (a) an LED (b) a resistor (c) a motor (d) a fuse
34. 34.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = I + R (c) V = I × R (d) V = R ÷ I
35. 35.🔺 A 0.4 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
36. 36.🔺 A 5.5 V supply is joined across a 220 Ω resistor. What current flows (in milliamperes, mA)?
37. 37.🧩 Which component boosts a small signal? (a) transistor (b) thermistor (c) LDR (d) motor
38. 38.🔺 A current of 10 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
39. 39.🔺 A current of 20 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
40. 40.💡 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) may burn out (b) lights up (c) does not light

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