The watt is a unit of measure of power in the SI system. Has Russian-language designation of W and foreign W. This unit in honor of the inventor James Uatt is called so. Now the power of all electric devices is measured in watts, this characteristic of power consumption can be found or on the device, or in the instruction to it.
It is required to you
- calculator
Instruction
1. The joule is a unit of measure of energy (work), power is connected with work as a formula: N = E / t where N is power in watts, E is energy in joules, t is time in seconds. That is, power is quantitatively equal in watts to the energy in joules spent in 1 second. So to transfer watts to joules per unit of time, you do not need even the calculator – look at device power in watts and you learn how many joules of energy it consumes in 1 second. However, it is impossible to call it translation per se – the power and energy are different physical quantities.
2. But not always power can be expressed in watts, there are also other units of measure of power. For example, the horsepower – unit of measure which became outdated and actually is not used in science. Though still engine capacity is specified in cars in horsepowers. To transfer horsepowers to watts, increase size in horsepowers by 735.5:1 hp = 735.5 watts
3. For determination of power of current in an electrical circuit you can use a wattmeter. In this device there are two measuring elements: consecutive and parallel coils. In the first coil the current proportional to loading, and in second proportional to mains voltage proceeds. Turn on the device in an electrical circuit according to the instruction and take from it readings of power in watts. Do transfer to joules as above. And if it is required to learn amount of the spent energy for the period bigger, than 1 second, then look for energy in joules so: E = N* t where N is power in watts, t is time in seconds.
4. But such way of the transfer of power to energy is not always fair, it concerns especially instant processes. For example, flash in a photographic studio. Even do not try to divide the specified energy of flash for a while – you do not receive the correct power but only in vain you will spend time. The same concerns also studio lighting. Here it is required to consider a set of various factors for determination of power of a light stream therefore for such purposes use devices fleshmeter (exposure meters), they will show results much more precisely.