A capacitor is a passive component made of two conductive plates separated by an insulator (called a dielectric). When voltage is applied across the plates, it creates an electric field in the dielectric — and this field stores energy. The property that describes this ability is called capacitance.

So remember:
Capacitance = ability to store energy in an electric field

This is often confused with inductance, which is the ability to store energy in a magnetic field. Both are ways of storing energy, but they work differently.

To help keep them straight:

• Capacitance → stores energy in an electric field
• Inductance → stores energy in a magnetic field

A helpful acronym: MICE
Magnetic → Inductance
Capacitance → Electric

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Tags: electronics definitions capacitance

The basic unit of capacitance, the Farad, is named for the physicist Michael Faraday.

The other units listed here are:

• the Volt - basic unit of voltage
• the Ohm - basic unit of resistance
• the Henry - basic unit of inductance

"Henry was Inducted into the hall of fame, and Faraday tipped his Cap(acitance)."

An additional memory aid: Many of us have heard of a Faraday Cage. Cages CAPture things (CAPacitance)

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Tags: electronics definitions capacitance

An inductor is a passive electronic component made by coiling wire — often around a core, which may be magnetic (like ferrite) or non-magnetic (like air), depending on the application. When current flows through the coil, it creates a magnetic field around it — and that magnetic field stores energy. The property that describes this ability to store energy in a magnetic field is called inductance.

This is a very common source of confusion:
Many people mix up inductance and capacitance because both refer to storing energy — but they store it in different types of fields.

To help keep them straight:

• Inductance → stores energy in a magnetic field
• Capacitance → stores energy in an electric field

A helpful acronym: MICE
Magnetic → Inductance
Capacitance → Electric

So for this question, the ability to store energy in a magnetic field is called inductance.

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Tags: electronics definitions inductance

An inductor is a passive electrical component that stores energy in a magnetic field; its unit is the henry, which is named for Joseph Henry.

It's good to know what the other units listed are as well, since they are all real units:

• the coulomb - unit of electric charge
• the farad - unit of capacitance
• the ohm - unit of resistance

Study Tip: Consider using the line "Henry was inducted into the hall of fame, and (Farad)ay tipped his Cap(acitance)" to jog your memory.

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Tags: electronics definitions inductance

Hertz is the standard unit for frequency, as used in the SI unit system. It is defined as the number of cycles per second of something periodic. For example a quartz clock ticks at \(1\)Hz. The wall outlet AC (in the US) is set to \(60\)Hz. The tone of A just below middle C is \(220\) Hz. The unit is named after Heinrich Hertz](wiki/Heinrich_Hertz). Here is a graphical example from Wikipedia.

The other (incorrect) answers here are:

• the farad - unit of capacitance
• the henry - unit of inductance
• the tesla - unit of magnetic field strength. \(31 µT\) (\(3.1 \times 10 − 5 T\)) - strength of Earth's magnetic field at 0° latitude (on the equator)

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Tags: frequencies definitions

RF is short for "Radio Frequency". The other listed options mean:

• AF - no meaning particular to ham radio, but could be AirForce
• HF - High frequency, commonly refers to frequencies between 3 and 30Mhz
• VHF - Very High Frequency, commonly refers to frequencies between 30Mhz and 300Mhz

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Tags: radio waves definitions

Electromagnetic waves are radio waves. Radio waves are typically denoted by electromagnetic wavelengths longer then Infrared. As with all electromagnetic waves, they travel at the speed of light.

The other wrong options:

• Gravity waves - wave that have the restoring force of gravity or buoyancy.
• Sound waves - a sound wave is a type of pressure wave.
• Pressure waves - propogate via particle collisions and is formed from alternating compressions and rarefactions.

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Tags: radio waves definitions

\[P={E}\times{I}\]

\[E=\frac{P}{I}\]

\[I=\frac{P}{E}\]

• P for Power (Watts)
• E for Electromotive Force (Voltage, Volts)
• I for Intensity (Current) (Amperes, Amps)

An easy way to remember is "Pixie". P I x E

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Tags: formulas math electrical power electrical current electromotive force (voltage) power law

\(P = I \times E\) \(=\) \(10 \times 13.8\) \(=\) \(138\) watts

The formula for electrical power is \(P = I \times E\).

"Power (in watts) equals Current (in amperes) multiplied by Potential Energy (in volts)."

\(P\) (watts) = \(10\) (amps)\(\times 13.8\) (volts)

\(10 \times 13.8 = 138\)

\(138\) watts

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Tags: math dc power electrical power electromotive force (voltage) electrical current power law

Power is the rate of of electrical energy generation or consumption.

\(P = V \times I\) (watts \(=\) volts \(\times\) amperes)

Where \(P\) is power (\(W\)), \(V\) is voltage (\(V\)), and \(I\) is current (\(A\)).

• \(P = I \times V\)
• \(V = 12V\)
• \(I = 2.5A\)

\(P = 12V \times 2.5A = 30W\)

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Tags: math dc power electrical power electromotive force (voltage) electrical current power law

We will use the Power Law, which is most commonly written as:

\[P = I \times E\]

We are given:

\(\begin{align} \text{(Power) } P &= 120\text{ watts}\\ \text{(Current) } I &= \text{?}\\ \text{(Voltage) } E &= 12\text{ volts}\\ \end{align}\)

To solve for \(I\) we can divide both sides by \(E\) and get

\(\begin{align} I &= \frac{P}{E}\\ I &= \frac{120}{12}\\ &= 10\text{ amperes} \end{align}\)

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Tags: math ohm's law electrical current electrical power