# Relate power rating of appliances to voltage and current relationship

### Voltage, Current and Resistance | HowStuffWorks

The relationship between voltage and current is defined (in ohmic devices like to the Hagen–Poiseuille equation, as both are linear models relating flux and that can then be used to power lights and appliances in homes and businesses. We've seen the formula for determining the power in an electric circuit — by multiplying the voltage in “volts” by the current in “amps” we arrive at an answer in “watts. relationship between power dissipation and current through a resistance. so commonly associated with the Ohm's Law equations relating voltage, current. Voltage, Power, Resistance and Current Press yourself at a point on your leg. appliance - which is essential for different power output from different appliances. What is the relationship between power, current and voltage? Together with resistance, they make up the Ohm's law that relates the three variables together.

If you plug in a light and it draws half an amp, it's a watt light bulb. Let's say that you turn on the space heater and then look at the power meter outside.

The meter's purpose is to measure the amount of electricity flowing into your house so that the power company can bill you for it.

Let's assume -- we know it's unlikely -- that nothing else in the house is on, so the meter is measuring only the electricity used by the space heater.

Your space heater is using 1. If you leave the space heater on for one hour, you will use 1. If your power company charges you 10 cents per kilowatt-hour, then the power company will charge you 12 cents for every hour that you leave your space heater on. Now let's add one more factor to current and voltage: We can extend the water analogy to understand resistance, too. The voltage is equivalent to the water pressure, the current is equivalent to the flow rate and the resistance is like the pipe size.

A basic electrical engineering equation called Ohm's law spells out how the three terms relate. Current is equal to the voltage divided by the resistance. This drop is due to inherent internal resistance within the source. The resistance is not due to an actual resistor, but can be modelled as such, and is composed of actual resistance of conductors, electronic components, electrolyte in batteries etc.

Examples of DC sources are batteries, DC generators known as dynamos, solar cells and thermocouples.

### Calculating Electric Power | Ohm's Law | Electronics Textbook

AC This stands for "alternating current" and means that the current "alternates" or changes direction. So current flows one way, reaches a peak, falls to zero, changes direction, reaches a peak and then falls back to zero again before the whole cycle is repeated. The number of times this cycle happens per second is called the frequency.

In other countries it is 50 Hz. The electricity supply in your home is AC. The advantage of AC is the ease by which it can be transformed from one voltage level to another by a device known as a transformer. AC sources include the electrical supply to your home, generators in power stations, transformers, DC to AC inverters allowing you to power appliances from the cigarette lighter in your carsignal generators and variable frequency drives for controlling the speed of motors.

The alternator in a vehicle generates electricity as AC before it is rectified and converted to DC. New generation brushless, cordless drills convert the DC voltage of the battery to AC for driving the motor. Reducing Costs of Transmitting Electricity Over the Grid Because AC can so easily be transformed from one voltage to another, it is more advantageous for power transmission over the electricity grid. Generators in power stations output a relatively low voltage, typically 10, volts.

Transformers can then step this up to a higher voltage, ,volts or higher for transmission through the country. A step up transformer, converts the input power to a higher voltage, lower current output. Now this decrease in current is the desired effect for two reasons. Power is wasted as heat in transmission cables, which obviously isn't wanted.

The AC waveform of the the domestic supply to our homes is sinusoidal. Source Transformer in an electrical sub-station. The function of a transformer is to either increase or decrease voltage. Source What is Three-Phase Voltage? Very long distance transmission lines may use DC to reduce losses, however power is normally distributed nationwide using a 3 phase system.

Each phase is a sinusoidal AC voltage and each of the phases is separated by degrees. So in the graph below, phase 1 is a sine wave, phase 2 lags by degrees and phase 3 lags by degrees or leads by degrees. Only 3 wires are needed to transmit power because it turns out that no current flows in the neutral for a balanced load. The transformer supplying your home, has 3 phase lines as input and the output is a star source so it provides 3 phase lines plus neutral.

## Calculating Electric Power

In countries such as the UK, homes are fed by one of the phases plus a neutral. In the US, one of the phases is split to provide the two 'hot' legs of the supply.

Why Is 3 Phase Used? More power can be transmitted using just 1. The incoming supply is typically 11kv and output phase voltage is volts in countries which use this voltage 3 Phase voltages.

Each phase is sinusoidal with a phase difference of degrees. Source Delta-Star Wye transformer which can supply single or 3-phase supply. Once we add a bulb to the circuit, resistance is created. There is now a local "blockage" or narrowing of the pipe, per our water pipe analogy where the current experiences some resistance.

## Watts, Amps and Volts Explained — Kilowatt Hours (Kwh) and Electrical Appliances

This greatly reduces the current flowing in the circuit, so the energy in the battery is released more slowly. As the battery forces the current through the bulb, the battery's energy is released in the bulb in the form of light and heat.

In other words, the current carries stored energy from the battery to the bulb, where it is turned into light and heat energy. The image above shows a light bulb as the main cause of electrical resistance. A watt is the base unit of power in electrical systems.

It can also be used in mechanical systems. It measures how much energy is released per second in a system. In our battery diagram, the size of both the voltage and the current in the bulb determine how much energy is released.