What does the power factor equal in an R-L circuit having a 60 degree phase angle between the voltage and the current?

0.5

From jordanm_78:

Power Factor = cos( ∢ phase angle)

In this case,

Power Factor = cos(60°)
Power Factor = 0.5

Last edited by markadlerdallas. Register to edit

Tags: none

If a resistance to which a constant voltage is applied is halved, what power dissipation will result?

Double.

From gsantee:

Using Ohm's Law equations:

Power (P) is equal to Resistance (R) times the Current (I) Squared.

• P= R x I²

Anytime R is halved, P will be halved as well.

Last edited by markadlerdallas. Register to edit

Tags: none

746 watts, corresponding to the lifting of 550 pounds at the rate of one-foot-per-second, is the equivalent of how much horsepower?

One horsepower.

The Imperial Horsepower of 746 watts is equivalent to 550 (550 ft-lbs/second), pounds at the rate of one-foot-per-second work.

1 Watt is 1 Newton-meter/second.

Converting from foot to meters, we get 1 foot of approximately 0.3048 meters.

1 pound = 0.454 kg = 0.454 ∗ 9.8= 4.492 N

So, we can determine that
550 ft/lb/s ∗ 0.3048 m/f ∗ 4.54 kg ∗ 9.8 Nm/s = 745.86 W
This shows that 550 ft/lb/s is equivalent to 746 Watts

By definition 1 HP is equal to 550 ft/lb/s

.

Last edited by markadlerdallas. Register to edit

Tags: none

In a circuit where the AC voltage and current are out of phase, how can the true power be determined?

By multiplying the apparent power times the power factor.

From kd9fni:

Power Factor = True Power ÷ Apparent Power

True power = Apparent Power ∗ Power Factor

Last edited by markadlerdallas. Register to edit

Tags: none

What does the power factor equal in an R-L circuit having a 45 degree phase angle between the voltage and the current?

0.707

From kd9fni:

Power factor = True Power ÷ Apparent Power.

If given an angle, calculate cos(45° degrees) = 0.707

Last edited by markadlerdallas. Register to edit

Tags: none

What does the power factor equal in an R-L circuit having a 30 degree phase angle between the voltage and the current?

0.866

From kd9fni:

Power factor = True power ÷ Apparent Power

It can also be calculated by taking the phase difference between the voltage and current, so:

cos(30° degrees) = 0.866

Last edited by markadlerdallas. Register to edit

Tags: none