Skip to content

Chapter 1 Quiz — Electric Charge and Basic Circuit Quantities

Multiple Choice Quiz

1. The fundamental unit of electric charge is the:

  • [ ] A) Ampere
  • [ ] B) Coulomb
  • [ ] C) Volt
  • [ ] D) Joule
Answer

B) Coulomb. The coulomb (C) is the SI unit of electric charge. One coulomb is equal to approximately 6.24 × 10¹⁸ elementary charges (the charge of a proton or the magnitude of the charge of an electron).

2. Electric current is defined as:

  • [ ] A) The energy stored in a circuit
  • [ ] B) The voltage difference between two points
  • [ ] C) The rate of flow of electric charge
  • [ ] D) The opposition to charge flow
Answer

C) The rate of flow of electric charge. Current \(I = dQ/dt\) — it is the rate at which charge moves past a point in the circuit. Its SI unit is the ampere (A), equal to one coulomb per second.

3. If a charge of 5 coulombs passes a point in 2 seconds, the current is:

  • [ ] A) 10 A
  • [ ] B) 7 A
  • [ ] C) 2.5 A
  • [ ] D) 0.4 A
Answer

C) 2.5 A. Using \(I = Q/t = 5\text{ C} / 2\text{ s} = 2.5\text{ A}\). One ampere is defined as one coulomb per second.

4. Which of the following correctly states Ohm's Law?

  • [ ] A) \(P = IV\)
  • [ ] B) \(V = IR\)
  • [ ] C) \(G = R\)
  • [ ] D) \(W = Pt\)
Answer

B) \(V = IR\). Ohm's Law states that the voltage across a resistor equals the current through it multiplied by its resistance. The other options are: P = IV (power equation), G = 1/R (conductance), W = Pt (energy equation).

5. A 6V battery is connected to a 2kΩ resistor. What current flows?

  • [ ] A) 12 mA
  • [ ] B) 3 mA
  • [ ] C) 0.3 mA
  • [ ] D) 300 mA
Answer

B) 3 mA. Using Ohm's Law: \(I = V/R = 6\text{ V} / 2000\text{ Ω} = 0.003\text{ A} = 3\text{ mA}\).

6. Power dissipated in a resistor can be calculated as:

  • [ ] A) \(P = V + I\)
  • [ ] B) \(P = V/I\)
  • [ ] C) \(P = I^2 R\)
  • [ ] D) \(P = R/V\)
Answer

C) \(P = I^2 R\). Power dissipated in a resistor is given by \(P = VI = I^2R = V^2/R\). All three forms are equivalent; use whichever is convenient given the known quantities.

7. In electrical circuits, "ground" refers to:

  • [ ] A) The physical Earth connection required for all circuits
  • [ ] B) The 0V reference point from which voltages are measured
  • [ ] C) The negative terminal of the battery
  • [ ] D) A short circuit condition
Answer

B) The 0V reference point from which voltages are measured. Ground (or electrical ground) is a conventional reference point assigned 0V. It does not need to be physically connected to Earth — it is simply the datum from which all other voltages in the circuit are measured.

8. An open circuit has:

  • [ ] A) Zero resistance and zero voltage
  • [ ] B) Infinite resistance and zero current
  • [ ] C) Zero resistance and maximum current
  • [ ] D) Finite resistance and maximum voltage
Answer

B) Infinite resistance and zero current. An open circuit is a break in the conduction path — effectively infinite resistance. No current can flow (\(I = V/\infty = 0\)), though a voltage may appear across the open gap.

9. A node in a circuit is defined as:

  • [ ] A) Any component that dissipates power
  • [ ] B) A closed loop through the circuit
  • [ ] C) A point where two or more circuit elements connect
  • [ ] D) The junction between series and parallel sections
Answer

C) A point where two or more circuit elements connect. A node is a connection point. All points connected by ideal (zero-resistance) wire belong to the same node — even if they appear as multiple physical junction points in a schematic.

10. A resistor is rated at 0.5W. If 200mA flows through it, what is the maximum resistance this rating allows?

  • [ ] A) 2.5 Ω
  • [ ] B) 12.5 Ω
  • [ ] C) 25 Ω
  • [ ] D) 100 Ω
Answer

B) 12.5 Ω. Using \(P = I^2 R\):

\[R = \frac{P}{I^2} = \frac{0.5\text{ W}}{(0.2\text{ A})^2} = \frac{0.5}{0.04} = 12.5\text{ Ω}\]

A resistance greater than 12.5 Ω at 200mA would exceed the 0.5W power rating.