Why all of the electrical devices are rated in voltage and not in current?

Answer 1

Voltage is a mesure of current

Answer 2

In fact, electrical devices are rated for both voltage and current (or sometimes wattage instead of current, which is within a multiplication of being the same thing). The voltage rating is the more important, as hooking a device to the wrong voltage can damage or ruin it. The current rating limits how many devices you can have on a single branch circuit.

Answer 3

There's a fairly simple answer for this. While it is current that can kill you, most people don't relate to Ohm's law and the relationship between Voltage, Current and Resistance, but they do relate to the levels of voltage we encounter in our daily lives. We all know about the 115V in the wall and the 230V for the dryer or the range and some of us have heard about the 408V on the pole that gets split and goes to our breaker box.

On many devices, there's a voltage rating first followed by the current rating (e.g. - Input 110-120 VAC, Output 12 VDC @ 200 mA).

I hope this helps.

Answer 4

You have to know what voltage the device was designed to use, because if you connect it to a circuit with too high a voltage, it will be destroyed, with lots of smoke and sparks resulting.

You don't need to know how much current it will draw, unless it draws too much for the circuit it is connected to, in which case the circuit's fuse will blow or the circuit breaker will switch off. Neither of these events will cause a fire.

Most devices have both the voltage and current ratings printed somewhere on them.

Answer 5

Use Ohms Law and work it out for yourself why you need both.

Voltage is variable according to the country. The higher the voltage the smaller the transmission cable for the same power.
Voltage is not in anyway shape or form, constant.
It even varies inside the Generating Station.
Outside you have Transmission Loses, Phase Distribution, Power Factor, Temperature, Line Losses etc and all contribute to voltage reduction.
I once paid £300 to obtain a static voltage for a variable five amp load. (Rotary Transformer.) Whatever that voltage was it varied each second without it.
Generating and Transmission is a HNC subject on its own.
Or it used to be 'x' years ago.
It is a constant battle to balance excitation, prime mover speed, and frequency at source, and that's before you put it on line.
At least you have one thing in your favour.
Theory and Practical are 99% the same and no empirical formulae.
Think yourself lucky friend

Answer 6

Current depends on the resistance of a device connected to a supply of particular voltage.

Supply voltage is different in different countries.If a device is connected to higher voltage system, the current flowing through will increase as resistance is same , thus spoling the device.

Answer 7

As an electrician for 45 years I have handled tens of thousands of electrical appliances, and have NEVER seen any without a rating plate or label stating the operating voltage, and current in either amps or watts/kilowatts. (except where the plate has been removed or come unstuck)

Voltage is the 'pressure' of the supply, current (amps) is the rate at which it flows, multiply the two, e.g. 240v X 5 amps = 1200 watts.

Answer 8

Most machines are rated in kW (kilo Watt) as this is what they consume. kilo Watt is a multiple of voltage and current. You can not vary the current of an electrical supply and countries have different voltages. Therefore the voltage is important as it will determine the current.

Answer 9

The supply voltage does not change. In the UK it is 250V in the US it is 120V. As ohms law states the current flowing in a circuit is directly proportional to the voltage and indirectly proportional to its resistance assuming the temperature remains constant. I=V/R. Thus if you have two devices with different internal resistances the current flow through each will change.

Answer 10

Because most power supplies run at a fixed voltage, or nearly-constant voltage. This is true of batteries, wall outlets, and DC adapters that plug into the wall outlet.

The current from these supplies can vary over a wide range.

Answer 11

In the uk all households have 230V; 13A sockets available.

All appliances will have a voltage, current and power rating all of which are connected by the formula P=V.I

eg Kettles are usually 2-3kW (= 8.7A-13.05A)

if the current isnt given then the power will be in most cases