A 12-volt source is connected across a 4-ohm resistor. What current flows through the resistor?
Ohm's Law
A 0.33 amp B 3 amps C 4 amps D 48 amps
Using Ohm's law, I = V ÷ R = 12 ÷ 4 = 3 amps.
Which electrical quantity is measured with an ohmmeter?
Measurement
A Current B Resistance C Power D Frequency
An ohmmeter measures electrical resistance, normally in ohms.
In electrical terminology, AC stands for
AC
A active circuit. B alternating current. C automatic charge. D ampere control.
AC means alternating current, in which the direction of current reverses periodically.
What is a basic function of a semiconductor diode?
Diodes
A To allow current mainly in one direction B To store mechanical energy C To increase wire resistance only D To measure voltage
A diode is designed to conduct current primarily in one direction and restrict it in the opposite direction.
Three resistors of 2 Ω, 3 Ω, and 5 Ω are connected in series. What is the total resistance?
Series Circuits
A 1 Ω B 5 Ω C 10 Ω D 30 Ω
Series resistances add directly: 2 + 3 + 5 = 10 Ω.
Two identical light bulbs are connected in parallel across an ideal voltage source. If one bulb burns out, what normally happens to the other bulb?
Parallel Circuits
A It also goes out immediately. B It continues operating. C It receives no voltage. D It becomes part of a series circuit.
In a parallel circuit, each branch has its own path to the source, so the other bulb can continue operating.
A device operates at 120 volts and draws 2 amperes. How much electrical power does it use?
Electrical Power
A 60 W B 118 W C 122 W D 240 W
Electrical power is P = V × I = 120 × 2 = 240 watts.
Which material is generally the best electrical conductor?
Conductors
A Copper B Rubber C Glass D Dry wood
Copper conducts electricity well and is commonly used for electrical wiring.
Why is plastic commonly used around electrical wires?
Insulators
A It increases current. B It acts as an electrical insulator. C It produces voltage. D It changes AC into DC.
Plastic has high electrical resistance and helps keep current from flowing where it should not.
What is the main purpose of a fuse in an electrical circuit?
Fuses
A To increase supply voltage B To open the circuit if current becomes excessive C To store electric charge D To convert resistance into current
A fuse melts and opens the circuit when current becomes dangerously high.
Which component is designed to store electric charge temporarily?
Capacitors
A Fuse B Capacitor C Switch D Transformer
A capacitor stores electric charge and electrical energy in an electric field.
A transformer is primarily used with AC circuits to
Transformers
A change voltage levels. B measure resistance. C store chemical energy. D produce mechanical friction.
Transformers use electromagnetic induction to step AC voltage up or down.
Electrical frequency is commonly measured in
Frequency
A ohms. B watts. C hertz. D volts.
Frequency is measured in hertz (Hz), meaning cycles per second.
Voltage is best described as
Voltage
A electrical potential difference. B opposition to current only. C the rate of cycles per second. D the physical size of a conductor.
Voltage is electrical potential difference, often thought of as the electrical 'push' that can drive current.
If voltage stays constant and resistance increases, what happens to current?
Resistance
A It increases. B It decreases. C It becomes resistance. D It always stays exactly the same.
From I = V ÷ R, increasing resistance while voltage stays constant causes current to decrease.
A typical battery supplies
Batteries
A direct current. B alternating current only. C mechanical current. D radio frequency only.
A battery provides DC, or direct current, with a fixed polarity at its terminals.
What is an important purpose of grounding electrical equipment?
Grounding
A To provide a safer path for fault current B To double normal operating voltage C To eliminate all resistance D To increase frequency
Grounding can provide a low-resistance path for fault current and helps protective devices operate.
When a simple switch in a series circuit is open, the circuit
Switches
A has a complete path for current. B has a broken path, so current stops. C automatically becomes parallel. D has zero resistance everywhere.
An open switch breaks the conducting path, preventing current from flowing through the circuit.
A transistor can commonly be used as
Transistors
A an electronic switch or amplifier. B a mechanical fuse only. C a wire insulator. D a unit of resistance.
Transistors are semiconductor devices widely used for switching and amplification.
A 9-volt battery is connected to two equal resistors in series. Assuming ideal components, approximately how much voltage is across each resistor?
Series Voltage
A 2.25 V B 4.5 V C 9 V D 18 V
Equal series resistors divide the source voltage equally, so each has about 9 ÷ 2 = 4.5 volts.