# What is the power - the rate at which it supplies electrical energy?

• phy112
In summary, the conversation discusses the use of a solar cell to provide electrical energy. The cell has an emf of 0.70 V and supplies a constant current of 20.5 mA for 8.0 hours, resulting in an output of 413.3 J of electrical energy. The conversation also touches on the concepts of power and energy, with power being the rate at which energy is supplied and measured in watts. It is important to convert units before using them in calculations. The final calculation for power yields 0.0144 W.
phy112

## Homework Statement

A solar cell provides an emf of 0.70 V.
If the cell supplies a constant current of 20.5 mA for 8.0 h, how much electrical energy does it supply? 413.3 J
What is the power - the rate at which it supplies electrical energy?

## Homework Equations

P=work/time
units J/s
i keep getting .014

## The Attempt at a Solution

Indeed. Is the 413.3 correct? I'll run a calculation n see what I come up with.

Use P = IV to find the power (current in Amperes x potential in Volts).
Electric potential is sometimes called "electromotive force" or "voltage".

Energy is Pt (power x time).
These concepts are often confused with each other. Power is the rate at which energy is provided (or work is done). It is measured in units of Joules per second (also called watts).

Don't forget to convert your mA into A, hours into seconds before using them!

That's what I get too, 0.0144 W. The energy (413.3 J) per time (8hrs = 8*60*60 secs).

Thanks!

## 1. What is the definition of power in terms of electricity?

The power of an electrical system is the rate at which it supplies or uses energy. It is measured in watts (W) and is calculated by multiplying the voltage (V) by the current (I).

## 2. How is power different from energy?

While power and energy are related, they are not the same thing. Power refers to the rate at which energy is being used or supplied, while energy is the total amount of work that can be done. In other words, power is the speed at which energy is being used or produced.

## 3. How is power important in everyday life?

Power is essential for our daily lives as it is used to operate various appliances and devices such as lights, electronics, and kitchen appliances. It is also necessary for industries to run machinery and for transportation to function. Without power, our modern way of life would not be possible.

## 4. How does power affect the cost of electricity?

The rate at which electricity is supplied or used, which is measured by power, directly affects the cost of electricity. The higher the power demand, the more energy is being used, resulting in a higher cost. This is why it is important to be mindful of our power usage to save energy and reduce electricity costs.

## 5. Can power be converted into other forms of energy?

Yes, power can be converted into other forms of energy, such as mechanical, thermal, or chemical energy. For example, a power plant converts the energy from burning fuel into electrical energy, which can then be used to power homes and businesses. Similarly, a generator converts mechanical energy into electrical energy.

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