Resistance and Ohms Law

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Electric current heats any material in which it
exits. Electric charges (electrons) collide with
each other. This way electric energy turns into
heat, or dissipate. Every material at room
temperature (20oC) has certain resistance due to
the current carriers collisions.
Resistance and Ohms Law
http//micro.magnet.fsu.edu/electromag/java/filame
ntresistance/
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Cu1.73 , Al 2.73 , Ag (silver)1.63
, C(coal) 2.7 , Teflon, sand, isolators..
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Resistors are marked according to the color code
(p41).
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Power (in W)
Jouleslaw
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2.21 (p63) For the circuit from Fig. determine
the power absorbed by the variable resistor R,
raging from 0-20ohms. Plot P(R).
Short circuit is dangerous because it can burn
the circuit
Voltage source delivers maximum power when the
resistance of the load is equal to the internal
resistance of the non-ideal source.
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Energy conservation law
2.30 (p64) For the circuit shown, find a)
currents I1 and I2, b) power delivered by the 3A
circuit source and the 12V voltage source, c)
total power dissipated by the circuit. Given
R125 W, R210 W, R35 W, R47W.
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Series resistors
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The Voltage divider rule
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Parallel resistors
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The Current divider
For two resistors only
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2.50 (p68) Determine the voltage between the nods
A and B in the circuit. Given Vs5V, R12.2k,
R218k, R34.7k, R43.3k.
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HW1! Due next Monday! Quiz 1! Next Monday!