Examples of power in the following topics:
-
- In physics, power is the rate of doing work—the amount of energy consumed per unit time.
- In physics, power is the rate of doing work.
- Power implies that energy is transferred, perhaps changing form.
- A coal-fired power plant may produce 1,000 megawatts; 1 megawatt (MW) is 106 W of electric power.
- Tremendous amounts of electric power are generated by coal-fired power plants such as this one in China, but an even larger amount of power goes into heat transfer to the surroundings.
-
- It can be shown that the average power is
- (an equation derived by taking a time average of power, P(t) = I(t)V(t), over a period.
- Thus cosϕ is called the power factor, which can range from 0 to 1.
- Power factors near 1 are desirable when designing an efficient motor, for example.
- Power delivered to an RLC series AC circuit is dissipated by the resistance alone.
-
- We found from the homework that a shock often gives the electrons that bounce across it a power-law distribution of energies, such that
- If the range of the power-law distribution is sufficiently large (at least an order of magnitude) we can take $x_1\rightarrow 0$ and $x_2 \rightarrow \infty$ in (23) so that the integral is simply a constant and we find that the spectral distribution is also a power-law $\omega^{-s}$ with a power-law index of $s=(p-1)/2$.
- This power-law spectrum is valid essentially between $\omega_c(\gamma_1)$ and $\omega_c(\gamma_2)$.
-
- The energy used is the time integral of the electric power.
- Power isn't necessarily constant; it may vary over time.
- The general expression for electric power is then
- Note that a circuit element having a power profile that is both positive and negative over some time interval could consume or produce energy according to the sign of the integral of power.
- Formulate the relationship between the energy usage and the electric power
-
- In a circuit with a resistor and an AC power source, Ohm's law still applies (V = IR).
- Examples include the commercial and residential power that serves so many of our needs. shows graphs of voltage and current versus time for typical DC and AC power.
- Since the power supplied is P = IV, if we use the above expressions for I and V, we see that the time dependence of power is:
- To find the average power consumed by this circuit, we need to take the time average of the function.
- (b) A graph of voltage and current versus time for 60-Hz AC power.
-
- Sound Intensity is the power per unit area carried by a wave.
- Power is the rate that energy is transferred by a wave.
- Sound Intensity is the power per unit area carried by a wave .
- Power is the rate that energy is transferred by a wave.
- The equation used to calculate this intensity, I, is:$I=\frac PA$Where P is the power going through the area, A.
-
- An antenna is a device that converts electric power into radio waves, and vice versa.
- An antenna (or aerial) is an electrical device that converts electric power into radio waves, and vice versa.
- In reception, an antenna intercepts some of the power of an electromagnetic wave in order to produce a tiny voltage at its terminals.
- A common car antenna that converts electric power in the air into electromagnetic waves.
-
- We saw how a power-law energy distribution of electrons can yield a power-law energy distribution of photons.
- However, it is also possible to produce a power-law distribution of photons from a thermal distribution of electrons if the optical depth to scattering is low.
- This will also give some insight about how one gets power-law energy distributions in general.Let $A$ be the mean amplification per scattering,
-
- Because voltage and current are out of phase, power dissipated by the circuit is not equal to: (peak voltage) times (peak current).
- The fact that source voltage and current are out of phase affects the power delivered to the circuit.
- It can be shown that the average power is IrmsVrmscosϕ, where Irms and Vrms are the root mean square (rms) averages of the current and voltage, respectively.
- For this reason, cosϕ is called the power factor, which can range from 0 to 1.
-
- For example, what is the power output for a 60.0-kg woman who runs up a 3.00 m high flight of stairs in 3.50 s, starting from rest but having a final speed of 2.00 m/s?
- Her power output depends on how fast she does this.
- Because all terms are given, we can calculate W and then divide it by time to get power.
- Substituting the expression for W into the definition of power given in the previous equation, P=W/t yields
- Her power output depends on how fast she does this.