Current Electricity Current and Circuits Producing Electricity: electric current conventional current battery photovoltaic

Electric Circuits A closed loop of conductors………………….. Rates of Charge Flow and Energy Transfer Ampere Power P = IV

Resistance and Ohm’s law Resistance R = V / I I R V

Problem Solving Strategies 1. Draw battery on left side of page with + on top. 2. Draw the wire coming out of the positive terminal to the next device. 3. Follow the current path until you reach the negative terminal. 4. Check your work !

Using Electric Energy Heating a Resistor Recall: P = VI and V = IR Substituting: P = I 2 R

The power dissipated by a resistor is proportional to the square of the current that passes through it and its resistance. E = Pt E = I 2 Rt

Transmission of Electric Energy Thermal energy is at a rate represented by P = I 2 R Even the wires carrying the electricity from the power plant lose energy through thermal loss. Reduce through lower R Reduce through lower I

This can be accomplished in several ways: We can lower “R” by increasing the size of the cables. Advantages? Disadvantages? We can lower “I” by increasing the voltage and delivering the same amount of power. Advantages? Disadvantages?

The Kilowatt - Hour Electric energy used is measured as a rate of energy consumption in joules per second (watts) times the number of seconds it is operated. W s orJ s / s = J 1 kWh = (1000j/s)(3600s) = 3.6 X 10 6 J