
1.
By the Power Formula: I = P/V = 2Watts/5Volts = 0.4A (400mA)
2.
Again, by the Power Formula: V = P/I = 0.25W/0.5A = 0.5V
3.
a) Use power across a resistor: P = V2/R = 9volts2/10KOhms = 0.9mW
b) Can use Ohm's law, or the Power Formula to find that: I = P/V = 0.9mW/3V = 0.3mA
4.
a) Here, use the power across the resistor as: P = I2·R = 144(mA)2·100Ohms = 14.4mW
b) Using the Power Formula: V = P/I = 14.4mW/12mA = 1.2V
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