Flashcards in Electrical Energy And Power Deck (11)

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1

Q

What is Power?

A

Is the rate of doing work

2

Q

What is Power measured in?

A

Watts (W)

3

Q

What is the Power equation?

A

P = E/t

4

Q

In a electrical circuit what is E that is part of P = E/t?

A

Work done moving a charge

5

Q

What is the Power equation for electrical circuits?

A

P = IV

6

Q

Why does the Power = IV equation make sense?

A

- Potential Difference is defined as the work done per coulomb
- Current is defined as the number of Coulombs transferred per second
- So P.D x Current is work done per second, i.e Power

7

Q

Combining P = IV and V = IR together can give you more equations such as?

A

P = I*2 x R

P = V*2 / R

8

Q

Energy is easy to calculate if you know the […….]

A

Power

9

Q

If you want to work out total energy transferred what is the equation we use?

A

E = Pt

10

Q

By substituting in other equations what can E =Pt be?

A

W = IVt Or W = (V*2 / R)t Or W = I*2 x R x t

11

Q

How do you investigate the power output of an electric motor?

A

- Attach mass to the motor as shown and connect the motor to the circuit as shown
- Record the time taken for the motor to raise the mass a set distance (using a stopwatch and meter rule)
- Calculate the work done against gravity using ΔEgrav = mg Δh
- Calculate the Power output of the motor using P = W/t
- Can also investigate efficiently taking P.D reading and Current readings to calculate the Power using P = IV
- Use the equation Efficiency equation Efficiency = (useful power output / Total power input)
- Could also investigate, using this apparatus, to investigate wether the power input and power output of the motor varies with the laid attached to it by varying the mass.