Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 702 · 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 is measured in amperes (A)? (a) voltage (b) energy used each second (c) the push of a cell (d) current
2. 2.🧩 Which component limits the current? (a) transistor (b) fuse (c) buzzer (d) resistor
3. 3.🧩 Which component is a resistance knob? (a) potentiometer (b) buzzer (c) thermistor (d) transistor
4. 4.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 25 % (c) 0 % (d) 5 %
5. 5.💡 A blue LED uses 3 V and should get 10 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
6. 6.🧮 An 8 V battery is joined to 2 Ω and 6 Ω resistors in series. What current flows (in amperes)? =
7. 7.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
8. 8.💡 Does it save or waste electricity to leave the TV on standby? (a) saves electricity (b) wastes electricity
9. 9.🌈 A resistor has the colour bands orange, brown, brown. What is its value (in ohms)?
10. 10.💡 Does it save or waste electricity to run fans in empty rooms? (a) saves electricity (b) wastes electricity
11. 11.💡 A red LED uses 2 V and should get 20 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
12. 12.🔺 A 2.4 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
13. 13.💡 An LED is joined to a 5 V battery through a 330 Ω resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) lights up (b) does not light (c) may burn out
14. 14.⚡ Power tells us … (a) energy used each second (b) the colour of light (c) the size of a cell (d) the length of a wire
15. 15.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
16. 16.💡 Does it save or waste electricity to leave fridge door open? (a) saves electricity (b) wastes electricity
17. 17.📏 Voltmeter or ammeter: which one measures current? (a) ammeter (b) voltmeter
18. 18.What does a transistor do? (a) stores a little charge (b) glows using little power (c) is a resistance knob (d) boosts a small signal
19. 19.🧾 A 250 W appliance runs for 10 hours. How many units (kWh) of electricity does it use? =
20. 20.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 9000 Ω resistor? (a) white-black-brown (b) white-black-red (c) white-black-orange (d) brown-white-red
21. 21.🔺 A current of 3 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
22. 22.What does an LDR do? (a) lets current go one way (b) senses how bright it is (c) limits the current (d) stores a little charge
23. 23.🔺 A current of 0.2 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
24. 24.⚡ A device works on 24 V and takes 2 A. What is its power (in watts)? =
25. 25.🔺 A current of 40 mA flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
26. 26.Which of these is measured in ohms (Ω)? (a) the push of a cell (b) voltage (c) power (d) resistance
27. 27.🔺 A current of 0.1 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
28. 28.Which of these is measured in volts (V)? (a) voltage (b) energy used each second (c) resistance (d) current
29. 29.True or false: a thermistor senses how hot it is. (a) False (b) True
30. 30.🌈 A resistor has the colour bands orange, blue, yellow. What is its value in kilo-ohms (kΩ)? =
31. 31.📏 How many kilo-ohms (kΩ) is 6300 Ω? =
32. 32.🧮 Three equal 30 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
33. 33.True or false: on an LED, the shorter leg is the cathode (−). (a) False (b) True
34. 34.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
35. 35.🌈 Which band is read first on a resistor? (a) the widest gap (b) any band (c) the one nearest an end (d) the gold band
36. 36.🧮 Two equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
37. 37.🔍 Which is the odd one out? (a) unplug idle chargers (b) close the fridge quickly (c) use old filament bulbs (d) switch off empty rooms
38. 38.🔺 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
39. 39.🌈 A resistor has the colour bands violet, blue, yellow. What is its value in kilo-ohms (kΩ)? =
40. 40.💡 A red LED uses 2 V and should get 10 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?

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