Bredhurst Receiving and Transmitting Society

Advanced Radio Amateur Examination

Please wait this page has many graphics

Power in DC circuits

The maths in this topic is in relation to :-

P = V x I, V = I x R, P = V² / R, P = I² x R

Here we have siimple multiplication and division and also raising to the power of two or sqaring the number. The course will show you each item. The button to be presed will be shown but when numerals need to be entered they will be shown as figures the sceeen result will be shown at the end of in stages depending upon the calculation.

P = V x I	What is the power in watts with 10000V and 5 amps
	10000 5
V = I x R	What is the voltage in V if 5 amps passes through a resistance of 18000
	5 18000
	Convert 90000V to kV
	From the above stage press result 90kV
P = V2 / R	Find the power in watts with 125V and resistance 150
For this calculation we need to introduce another key try the following :- 5 result 25. So back to the question in hand :- Find the power in watts with 125V and resistance 150
	125 150
	convert to kW
	From the above stage press note the 06 indicating MW
	so press the again and we see the 03 indicating kW - result 2343.75 kW
If we wanted to get back to the 06 then press then - so this shows that you can go up and down the exponential until you find the correct level.
P = I2 x R	Find the power in kilo watts with 12.5 Amps and resistance 150
	125 150
Note :-that the conversion to the "engineering" value has to be done after the main calculation. The 03 indicates the kilo value 103 : Result 23.4375 kW
kilo 103 Mega 106 Giga 109

So that completes the calculations for this set.

There are more functions to show you but it is hoped that you have taken all the above onboard and it is time to give yourself a coffee / tea break !!!

Next Circuit theory