# Need help about math is my calculation wrong the answer from the text book is wrong

1. Feb 10, 2008

### Manelectro

I'm having a tough time wrapping my head around something that seems so simple. The Question is:

What is the maximum output power from a 12 volt battery that has an internal resistance of 6 ohm ?

The answer from this books is 6 W?

My formula
First I need to find the current
I = V/R so 12volt/6 ohm = 2 ampere

When is use this formula
P = VI, 12Vx2A = 24Watt,

The next question is:
On an oscilloscope display of a pure sine wave , the peak to peak value is 7 volts. The average value of the display voltage is about:

A. 6.36 volt
B.3.18 volt
C. 0 volt
D. 2.23 volt

The answer from this book is 0 volt.

The peak to peak voltage is 7/2 = 3.5V this peak voltage

But by calculation Vaverage = 2 x 3.5/ pi = 2.228 or 2.23 V for sine wave or AC wave formula.

If the average value were taken over the whole cycle then the result would be zero value.

Thank you,
Azman

2. Feb 11, 2008

### Manelectro

Anybody can answer this question. where the math guru...anyway thank :)

3. Feb 13, 2008

delet