Understanding AC and DC Circuits

Why is it significant that DC current flows in a single direction?

• It ensures devices operate consistently.

• It increases the voltage over time.

• It reverses polarity frequently.

• It reduces the lifespan of a circuit.

If you reverse the polarity of a DC battery in a motor circuit, what would most likely occur?

• The motor would stop working.

• The motor would spin faster.

• The motor would spin in the opposite direction.

• The motor would generate more heat.

Which of the following is a major advantage of using AC over DC for power transmission?

• AC is more efficient for low-power applications.

• AC can be easily converted between high and low voltages.

• AC ensures a constant flow of current.

• AC provides a fixed polarity for devices.

You are tasked with designing a circuit for a light bulb using an AC source. What additional components might you include to ensure safe operation?

• A resistor to regulate voltage.

• A switch to alternate polarity manually.

• A frequency converter to reduce cycles per second.

• An inductor to prevent current flow.

Why does the light bulb in an AC circuit dim and brighten cyclically?

• Due to fluctuations in current resistance.

• Because voltage alternates direction and magnitude.

• Because the bulb is designed for DC current.

• Due to changes in power consumption.

What happens to an incandescent bulb connected to a 60 Hz AC source?

• It flashes 60 times per second, visible to the human eye.

• It emits a constant light due to rapid flashes.

• It changes brightness depending on polarity.

• It only lights up during positive voltage cycles.

Considering energy efficiency, why might DC be chosen for electronic devices like laptops?

• It produces less heat during operation.

• It provides a constant voltage for stable performance.

• It is easier to generate than AC.

• It allows devices to change polarity as needed.

If you wanted to demonstrate the concept of AC frequency, which experiment would best illustrate it?

• Observing the spinning of a DC motor.

• Measuring light intensity changes in a bulb connected to AC.

• Measuring voltage decay in a battery over time.

• Connecting a capacitor to smooth out AC fluctuations.

How does the graph of voltage over time differ between AC and DC circuits?

• DC voltage remains constant, while AC voltage varies sinusoidally.

• AC voltage remains constant, while DC voltage fluctuates.

• Both AC and DC voltage show periodic peaks and valleys.

• DC voltage alternates direction, unlike AC voltage.

How can you calculate the frequency of an AC system?

• By counting the voltage peaks in one second.

• By measuring the steady voltage level over time.

• By observing the direction of current flow.

• By timing how long it takes for the current to stabilize.