Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 3 · 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 home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
2. 2.🔺 A current of 0.5 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
3. 3.🔺 A current of 50 mA flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
4. 4.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 5 V supply. What current flows (in mA)?
5. 5.📏 How many milliamperes (mA) is 0.67 A?
6. 6.🧩 Which part changes electrical energy into sound? (a) a capacitor (b) a buzzer (c) a diode (d) a resistor
7. 7.🧩 Which component makes a beeping sound? (a) diode (b) potentiometer (c) LDR (d) buzzer
8. 8.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
9. 9.True or false: the voltmeter measures current. (a) True (b) False
10. 10.🌈 A resistor has the colour bands grey, yellow, orange. What is its value (in ohms)?
11. 11.🧩 Which component limits the current? (a) diode (b) motor (c) transistor (d) resistor
12. 12.True or false: on an LED, the shorter leg is the cathode (−). (a) False (b) True
13. 13.True or false: a thermistor blows if current is high. (a) False (b) True
14. 14.📏 How many watts (W) is 4.1 kW?
15. 15.🔺 An 8 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
16. 16.🌈 Which band is read first on a resistor? (a) any band (b) the one nearest an end (c) the widest gap (d) the gold band
17. 17.🔺 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
18. 18.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
19. 19.📏 How many kilo-ohms (kΩ) is 5900 Ω? =
20. 20.📏 How many kilo-ohms (kΩ) is 9700 Ω? =
21. 21.🌈 A resistor has the colour bands red, blue, black. What is its value (in ohms)?
22. 22.🌈 In the resistor colour code, which number does violet stand for?
23. 23.🌈 In the resistor colour code, which number does brown stand for?
24. 24.🧮 Two resistors in parallel give a total that is … (a) always zero (b) less than either one (c) more than either one (d) their sum
25. 25.💡 Does it save or waste electricity to set the AC to 24 °C? (a) saves electricity (b) wastes electricity
26. 26.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 50 % (c) 0 % (d) 5 %
27. 27.🔺 A current of 10 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
28. 28.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) becomes zero (c) gets bigger (d) gets smaller
29. 29.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = I ÷ V (c) R = V ÷ I (d) R = V + I
30. 30.🌈 A resistor has the colour bands blue, white, yellow. What is its value in kilo-ohms (kΩ)? =
31. 31.📏 How many amperes (A) is 40 mA? =
32. 32.🧮 Resistors of 150 Ω, 50 Ω, 150 Ω and 330 Ω are joined in series. What is the total resistance (in ohms)?
33. 33.🧾 A family uses 100 units of electricity in a month and each unit costs ₹5. What is the bill (in ₹)?
34. 34.🌈 In the resistor colour code, which number does blue stand for?
35. 35.What does a motor do? (a) smooths a wobbly supply (b) is a resistance knob (c) lets current go one way (d) turns a fan or wheels
36. 36.🔺 A current of 20 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
37. 37.🔺 A current of 0.1 A flows when 1.2 V is joined across a resistor. What is its resistance (in ohms)?
38. 38.📏 Which unit measures power? (a) ampere (A) (b) ohm (Ω) (c) volt (V) (d) watt (W)
39. 39.📏 Voltmeter or ammeter: which one is joined in series? (a) voltmeter (b) ammeter
40. 40.💡 Does it save or waste electricity to use LED lamps? (a) wastes electricity (b) saves electricity

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