1-this is what is written in my book:E= Ir+E' where E' is the back

[brainyman89]

1-this is what is written in my book:
E= Ir+E' where E' is the back emf, r and E' are constants
P(mechanical)=E'*I
an electrical motor functions only if the generator connected across its terminals delivers a positive potential difference that exceeds its back emf.
So my question is, why are they regarding the back emf as constant quantity that characterizes each motor though the current across the motor is not always constant?

2-"in case we connected a pure inductor(coil) to AC generator, during a part of the cycle, energy is actually transferred from the inductor (load) back into the voltage source. we get a net power dissipation of zero."
how could energy be transferred to a generator??
in this case, a current is traversing the circuit without dissipating energy, will the current traversing the coil in this situation has a very large intensity as the case of a short circuit?

3-is there any proof why the average power equals cosine the phase angle (Φ) between voltage and current(case of sinusoidal voltage)?

4-does the back emf in motors have sinusoidal form?

5-P(mechanical)=E'*I where E' is the back emf
is this formula of mechanical power converted by the motor right??

6-does the electrical energy converted to mechanical energy by the motor increase when the motor is loaded? will the intensity of the traversing current increase?

7-in case a motor is loaded, will the mechanical power converted by the motor be smaller although the intensity of current has increased??
since P(mechanical)=E'*I where E' is the back emf, E' decreases when the motor is loaded?

8-what causes Inrush current drawn by an electrical device when first turned on in case we are supplying the device AC current?

9-why does the capacitor gets the same voltage of the generator after it is disconnected?

10-i have understood how a capacitor stores charge, but my question is how does capacitor stores energy? is storing charge the same as storing energy?

 

[asdofindia]

10) Capacitor stores energy in the form of electric field in between the plates. (Field has energy associated with it!)

 

[brainyman89]

anybody?

 

[asdofindia]

2-how could energy be transferred to a generator??

Does that really happen. I thought that a current flowed through the generator (which wasn't generated by the generator)

3-is there any proof why the average power equals cosine the phase angle (Φ) between voltage and current(case of sinusoidal voltage)?

I have one in my textbook.

4-does the back emf in motors have sinusoidal form?

I think yes.

5-9

i replied just because nobody else was replying.

 

[PJC01]

1. The back emf, E', is typically considered a constant quantity because it is determined by the design and construction of the motor. It is not affected by the varying current across the motor. The current, however, can vary depending on the load on the motor. This is why it is important for the generator to deliver a positive potential difference that exceeds the back emf in order for the motor to function.

2. In this case, the energy is not being transferred to the generator, but rather back into the voltage source. The inductor acts as a temporary storage for energy, releasing it back into the circuit as the current changes direction. The current in this situation will not be as high as a short circuit, as there is still some resistance in the circuit.

3. The proof for why the average power equals cosine of the phase angle between voltage and current for a sinusoidal voltage is based on the mathematical calculation of power using complex numbers. It is beyond the scope of this response to provide a detailed explanation, but it can be found in most textbooks on AC circuits.

4. The back emf in motors does not have a sinusoidal form. It is typically a straight line, but can vary depending on the design of the motor.

5. Yes, the formula P(mechanical)=E'*I is correct for calculating the mechanical power converted by the motor.

6. When a motor is loaded, the electrical energy converted to mechanical energy will increase, but the intensity of the current may not necessarily increase. This depends on the design of the motor and the load on it.

7. Yes, the mechanical power converted by the motor may be smaller when it is loaded, even though the current may have increased. This is because the back emf, E', will decrease as the motor is loaded, leading to a decrease in the mechanical power output.

8. Inrush current is caused by the initial surge of current needed to charge the capacitors and magnetic elements in the device. This is because these elements initially have no charge or magnetization, and require a large current to reach their steady state.

9. When a capacitor is disconnected from the generator, it will still retain the same voltage because it acts as a temporary storage for energy. The voltage across the capacitor will remain the same until it is discharged.

10. Storing charge and storing energy are not the same thing. A capacitor stores energy by storing charge on its plates. When a voltage is applied,