OAR OAR Mechanical Comprehension: Electricity 4 — Questions and Answers
Question 1: A 60W bulb and a 100W bulb are connected in series. Which bulb glows brighter?
- The 100W bulb
- The 60W bulb (Correct answer)
- They glow equally
- Neither glows
Correct answer: The 60W bulb
In series, the same current flows through both; the 60W bulb has higher resistance and dissipates more power (P = I²R).
Question 2: What is the relationship between frequency and period of an AC waveform?
- f = T
- f = 1/T (Correct answer)
- f = T²
- f = 2T
Correct answer: f = 1/T
Frequency and period are reciprocals: f = 1/T, where T is the time for one complete cycle.
Question 3: What happens to resistance as the temperature of a metal conductor increases?
- Resistance decreases
- Resistance increases (Correct answer)
- Resistance stays constant
- Resistance becomes zero
Correct answer: Resistance increases
In metals, higher temperature increases atomic vibration, impeding electron flow and raising resistance.
Question 4: A 12V circuit draws 3A. A second identical load is added in parallel. What is the new total current?
- 3A
- 6A (Correct answer)
- 1.5A
- 9A
Correct answer: 6A
Each parallel branch draws 3A, so total current doubles to 6A with two identical loads.
Question 5: What is the standard frequency of AC power in the United States?
- 50 Hz
- 60 Hz (Correct answer)
- 120 Hz
- 25 Hz
Correct answer: 60 Hz
US power grids operate at 60 Hz, meaning alternating current completes 60 cycles per second.
Question 6: Which of the following best describes an electrical insulator?
- A material that allows easy electron flow
- A material that opposes electron flow strongly (Correct answer)
- A material that stores charge
- A material that converts AC to DC
Correct answer: A material that opposes electron flow strongly
Insulators have very few free electrons and high resistance, preventing significant current flow.
Question 7: In a parallel circuit, if one branch is open (broken), what happens to the other branches?
- All branches stop working
- The other branches continue operating normally (Correct answer)
- Voltage drops to zero
- Current doubles in remaining branches
Correct answer: The other branches continue operating normally
In a parallel circuit, each branch is independently connected to the voltage source, so other branches are unaffected by an open branch.
OAR OAR Mechanical Comprehension: Electricity 4
A 60W bulb and a 100W bulb are connected in series.
Which bulb glows brighter?