KCL Current Law calculations

kirchhoffs-laws

I hope you can help in relation to my KCL question which asks that I find the currents in i1, i2, i3 and is.

I'll also need to calculate the power dissipated by the resistors in the circuit and confirm that the power dissipated by the resistors is the same as the power supplied by the power source.

I have done some calculations below but I'm not sure if I'm doing this correctly.

$$I1 = 20 I= V/R = 0.25A = 1.25W$$

$$I2 = 40 I= V/R = 0.125A = 0.625W$$

$$I3 = 80 I= V/R = 0.0625A = 0.3125W$$

$$Is = 10 I= V/R = 0.5A = 2.5W$$

Power dissipation = I(amps) x V

Thanks.

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Best Answer

Sanity check

Current from 5V supply is \$\dfrac{5V}{10\Omega + parallel resistors}\$

Parallel resistors are \$\dfrac{1}{\frac{1}{20}+\frac{1}{40}+\frac{1}{80}}\$ = 11.43 ohms

Therefore current is \$\dfrac{5V}{21.43\Omega}\$ = 233.33 mA and this means total power is 1.1667 W.

Voltage across the three parallel resistors = 5V - \$10\Omega\times 0.23333 = 2.6667V\$

From this you can calculate the currents in the individual resistors.

This is what you should be getting whatever method you use.

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