# Gadget Savvy: Capacitors Quiz

1 min
Image: Tim Ridley/Dorling Kindersley/Getty Images

What looks like a battery, has two terminals like a battery and stores electrons like a battery? Capacitors can store and release electrical energy, but don't replenish their supply. How do capacitors work, and what tools rely on them?
What do capacitors store?
protons
electrons
neutrons

In a way, capacitors are like batteries. Although they work in completely different ways, capacitors and batteries both store electrical energy in the form of electrons.

What separates the two terminals inside a capacitor?
metal
nonconductive material
water

Inside the capacitor, the terminals connect to two metal plates and are separated by a nonconducting substance, called a dielectric.

What types of devices do air capacitors usually power?
timing circuits
antennas

Mylar capacitors are commonly used for timing circuits, while ceramic ones are used for antennas. Air capacitors power radio tuning circuits.

If you charge a capacitor using a 1.5-volt battery, how much voltage will the capacitor gain?
0 volts
1.5 volts
3 volts

Once it's charged, the capacitor has the same voltage as the battery -- in this case, 1.5 volts.

Which of these is a natural example of a capacitor?
fire
snow
lightning

Nature shows the capacitor at work in the form of lightning. One plate is the cloud, the other plate is the ground, and the lightning is the charge released between these two.

What unit of measurement is used when referring to a capacitor's storage potential?
volts
coulombs

A capacitor's storage potential, or capacitance, is measured in units called farads.

What's the primary difference between a capacitor and a battery?
Capacitors can store more electrons than batteries.
Capacitors hold the same amount of power as batteries, just in a smaller volume.
Capacitors can drain their electrons faster than batteries.

The difference between a capacitor and a battery is that a capacitor can dump its entire charge in a fraction of a second, whereas a battery would take minutes to completely discharge.

Is a camera's electronic flash powered by a battery or a capacitor?
battery
capacitor
neither

A camera's electronic flash uses a capacitor. The battery charges up the flash's capacitor over several seconds, and then the capacitor dumps the full charge into the flash tube almost instantly.

Why are charged capacitors dangerous?
They can leak harmful chemicals.
They can cause loss of vision.
They can release a lethal charge.

Large, charged capacitors are extremely dangerous, which is why flash units and TVs have warnings about opening them up. These products contain big capacitors that can, potentially, kill you with the charge they contain.

What invention is generally referred to as the first capacitor?
Leyden jar
Kleist jar
Mason jar