OAR Mechanical Comprehension: Electricity Questions and Answers — Questions and Answers
Question 1: A simple circuit consists of a battery and three light bulbs connected in series. If the middle bulb's filament breaks, what will happen to the other two bulbs?
- They will both go out. (Correct answer)
- They will both get brighter.
- The first bulb will stay lit, but the last one will go out.
- They will both get dimmer, but stay lit.
Correct answer: They will both go out.
In a series circuit, there is only one path for the current to flow. A burned-out bulb creates an open break in this path, stopping the flow of current to the entire circuit, so all bulbs will go out.
Question 2: According to Ohm's Law, if the voltage in a circuit is doubled while the resistance remains constant, what is the effect on the current?
- It is halved.
- It is quadrupled.
- It is doubled. (Correct answer)
- It remains the same.
Correct answer: It is doubled.
Ohm's Law states that Voltage (V) = Current (I) × Resistance (R). This means that current is directly proportional to voltage. If the voltage is doubled and resistance is unchanged, the current must also double to maintain the relationship (2V = 2I × R).
Question 3: The wiring in a house allows a lamp in one room to be on while a television in another room is off. This indicates that the house's circuits are wired in which configuration?
- A series circuit
- A parallel circuit (Correct answer)
- A short circuit
- An open circuit
Correct answer: A parallel circuit
In a parallel circuit, each electrical device is on a separate branch, allowing for multiple paths for the current. This enables each device to operate independently. If one device is turned off or fails, the others remain operational.
Question 4: Which of the following best describes the primary function of a fuse in an electrical circuit?
- To increase the voltage for connected devices.
- To store a small amount of electrical charge.
- To convert direct current (DC) to alternating current (AC).
- To protect the circuit from excessive current. (Correct answer)
Correct answer: To protect the circuit from excessive current.
A fuse is a safety device containing a wire designed to melt and break the circuit if the current exceeds a safe level. This sacrificial action protects the circuit's components from damage due to overcurrents or short circuits.
Question 5: An electrical device uses 600 watts of power when connected to a 120-volt source. What is the current flowing through the device?
- 2 amperes
- 72,000 amperes
- 5 amperes (Correct answer)
- 0.2 amperes
Correct answer: 5 amperes
The formula for electrical power is Power (P) = Voltage (V) × Current (I). To find the current, rearrange the formula to I = P / V. Therefore, Current = 600 watts / 120 volts = 5 amperes.
Question 6: Which of the following materials is the best electrical insulator, meaning it most effectively resists the flow of electricity?
- Copper
- Aluminum
- Sea water
- Rubber (Correct answer)
Correct answer: Rubber
An electrical insulator is a material in which electrons are not free to move, thus preventing the flow of electric current. Rubber is an excellent insulator and is commonly used to cover wires for safety. Copper, aluminum, and sea water are all electrical conductors.
OAR Mechanical Comprehension: Electricity Questions and Answers
A simple circuit consists of a battery and three light bulbs connected in series.
If the middle bulb's filament breaks, what will happen to the other two bulbs?