To determine the amperage demand, divide the watts of a specific electrical item by the entire number of volts accessible from the electric outlet. Amperes, or amps, are used to quantify the amount of current flowing through the wire. The more amps, the faster the flow of current and the more powerful the item. A circuit breaker prevents overloads and other damage caused by excessive currents.

There are about 15 milliamperes (mA) available in **an 120-volt circuit**. If you need 100 mA, that's 1 amp. 300 mA is 3 amps. 600 mA is 6 amps. 900 mA is 9 amps. Etc.

So if you want to find out how much current is running through a lamp, simply divide its wattage by the voltage of the circuit it's on. For example, if a lamp requires 10 watts but uses 120 volts, then it's using **10/120 or 0.083 amps**.

Lamps tend to be specified by **their ampere rating**. This is the maximum amount of current that will flow through the lamp when it's on full power. For example, a 20-watt lamp can supply 20 watts at a time, so it has **a maximum ampere rating** of 20 x 120 = 2400 mA.

To calculate the required amperage, divide the number of watts by the number of volts. A 120-watt item using 1,200 volts, for example, needs 10 amps. A 240-watt item using 240 volts needs 20 amps.

Amps equal **current times volts**, so this is simply calculating the amount of time it will take for the circuit to drain the battery. If you don't want to use batteries, then an energy supply that is strong enough to drive the load for more than one hour is necessary. For example, if a light bulb consumes **100 watts** and requires at least 12 volts to operate, then it will need at least 12 amps for more than one hour. Diodes don't allow current to flow in their reverse direction, so they can be used as open circuits or short circuits by choosing different pins to connect to either terminal. For example, if you wanted the diode to conduct only forward current but not backward voltage, you could connect its anode to **a positive power source** and its cathode to the load. Any additional diodes placed in parallel with the first one would also have to be connected together in the opposite direction, otherwise there would be no current flow.

Diodes do require some force to push them into connection, so they should never be directly connected together or else damage will occur.

Calculator for converting electric current in amps (A) to **electric power** in watts (W). Select the current type, input the current in amps, voltage in volts, and power factor for the alternating current circuit, then click the Calculate button (DC = Direct Current, AC = Alternating Current): For scientific notation, use e.g. 1.0e-01 instead of 0.100000.

Watts Calculation Watts are calculated by multiplying amps by the line voltage, which is commonly 120 V in **the United States**. For example, if the label on your portable electric heater states it draws **8.35 amps** when turned on, multiply 8.35 amps by 120 V to get around 1,000 watts of demand. The more amps a device pulls when switched on, the higher its wattage rating will be.

The term "wattage" comes from the old unit of power measurement, the watt. One watt is enough power for one amp flowing through a resistance of one ohm. Because batteries have internal resistances, less than one amp will usually flow through them at a time. To determine how much battery power is available for use, divide the load current by the battery's series resistance or internal impedance. For example, if a flashlight's bulb consumes 0.5 amp while charging, then its battery has 5,000 milliwatts (0.005 amp) available to run the light when it's turned off.

In practice, however, we need a way to measure power over time, not just an instantaneous reading. To do this, most devices include **some sort** of **watt-hour meter** or power indicator that shows us how much energy is being used. They can tell us how much power is being consumed as well as how long it takes to consume that amount of power.

These indicators come in two forms: analog and digital.