Which electrical component only permits current to flow in one direction?

Which electrical component only permits current to flow in one direction?

• A. Diode
• B. Resistor
• C. Capacitor
• D. Inductor

Answer: (A)

One-way current flow is a defining feature of a diode. A diode is a two-terminal semiconductor device that conducts readily in the forward direction when its anode is more positive than its cathode, and blocks current in the reverse direction. This behavior comes from the PN junction: in forward bias the potential barrier lowers so charge carriers can cross and produce current; in reverse bias the barrier is kept high, preventing most current from flowing. That’s why diodes are used for rectification and to protect circuits from reverse polarity. Resistors simply resist current and work in either direction, following Ohm’s law. Capacitors pass current briefly while they charge or discharge but block steady direct current, so they aren’t inherently one-way devices. Inductors respond to changes in current and can carry current in either direction, with their effect depending on frequency.

One-way current flow is a defining feature of a diode. A diode is a two-terminal semiconductor device that conducts readily in the forward direction when its anode is more positive than its cathode, and blocks current in the reverse direction. This behavior comes from the PN junction: in forward bias the potential barrier lowers so charge carriers can cross and produce current; in reverse bias the barrier is kept high, preventing most current from flowing. That’s why diodes are used for rectification and to protect circuits from reverse polarity.

Resistors simply resist current and work in either direction, following Ohm’s law. Capacitors pass current briefly while they charge or discharge but block steady direct current, so they aren’t inherently one-way devices. Inductors respond to changes in current and can carry current in either direction, with their effect depending on frequency.