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VK3ABK > TECH 16.10.06 11:02l 40 Lines 1391 Bytes #999 (0) @ WW
BID : 41391_VK3HEG
Read: GUEST DL1LCA OE7FMI
Subj: Re: Physics problem (DK2ZA)
Path: DB0FHN<DB0RGB<DB0MRW<DK0WUE<SP7MGD<VK7AX<VK3HEG
Sent: 061016/0453Z @:VK3HEG.#WEV.VIC.AUS.OC #:41391 [Ballarat] $:41391_VK3HEG
From: VK3ABK@VK3HEG.#WEV.VIC.AUS.OC
To : TECH@WW
Hello maths grads.
The 'physics problem' from Helmut, DK2ZA, seems to be more a 'lesson in logic'
as much as a test of Ohm's law. The question is what is meant by 'maximum'
power; is it in the circuit, or in 'each' resistor. This could confuse a
student, and demonstrates the importance of reading and understanding the
question. Always most important in an examination.
Now, to jump in, and hope I have done what I say, Here is my solution.
ÚÄÄÄÄÄÄÄÄÄ7.07vÄÄÄÄÄÄÄÄÄ¿ Applied voltage
³ ³
³ 10 ³
ÃÄÄÄÄÄÄ/\/\/\/\/\ÄÄÄÄÄÄÄ´ 10 Ohm 5 Watt
³ 20 ³
ÃÄÄÄÄÄÄ/\/\/\/\/\ÄÄÄÄÄÄÄ´ 20 Ohm 2.5 Watt
³ 30 ³
ÀÄÄÄÄÄÄ/\/\/\/\/\ÄÄÄÄÄÄÄÙ 30 Ohm 1.667 Watt
Total power from the 7.07 Volt supply...5 + 2.5 + 1.667 = 9.167 Watt
Voltages for 'maximum' resistor rating (5W) would require a voltage divider
but I guess that is not the aim of the question.
For the... 10 Watt resistor 7.707 Volt
20 Watt resistor 10 Volt
30 Watt resistor 12.24 Volt
Voltages and Wattage approximate to calculator standards.
Or have I misunderstood the question!
73. Dick. VK3ABK.
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