Physics S.O.S 1. 2. 3. 4. Electric Current and Direct Current Circuit| 3 Power and Electrical Energy Terminal Voltage Kirchhoff’s law Potentiometer & Wheatstone Bridge Theory Electrical energy Work done to move the charge from one terminal to the other W=qV E =IVt Electrical power Rate of work done or rate of energy transfer P= Power and Electrical Energy Formula Electrical Energy E = IVt Examples Electrical Power P = IV P= I2R P= Power dissipated by a resistor I = Current through the resistor V = voltage across the resistor R = Resistance of the resistor 1. Energy delivered to the circuit in 1 minute 2. Power delivered to the circuit 3. Power dissipated by the 4Ω resistor 480 J,8W,1.77W Terminal Voltage V = ε - Ir VT = V supplied 1. Current in the circuit 2. Determine the terminal to the circuit V = ε - Ir Kirchhoff’s Law Junction Rule ∑ 1. Draw the direction of current at the junction 2. Write the equation for the junction rule 3. Draw the direction of e.m.f on the battery. ∑ Loop/voltage Rule ∑ Step ∑ voltage of the battery 0,75A,4.5 V 4. Draw the loop, choose any direction you like 5. Write down the equations for both loops. 6. Solve the equation. Loop = current & e.m.f 1. Current in 3Ω resistor 2. Total current in the circuit 3. Terminal voltage of the battery 4. Internal resistance of cell 5. Power dissipated by 5Ω 6 A; 9 A; 63 V; 1;405 W Physics S.O.S Potential Divider Electric Current and Direct Current Circuit| 3 R1 V V1 R1 R2 R2 V V2 R1 R2 l V1 1 V l1 l2 l V2 2 V l1 l2 Determine unknown e.m.f Given that R1 = 6Ω and R2 = 8Ω and e.m.f of the cell is 28 V. Determine the voltage across 6Ω. 12V Determine the internal resistance of a cell Determine the voltage across 8Ω V8Ω = 5.33 V Potentiometer Determine the voltage across 30cm. V30cm =2.16 V Wheatstone Bridge R1 R2 R3 Rx Rx R LAL LJB Determine: 1. 2. Potential difference across the 6.7 resistor, 3. Power dissipated from the 1.2 resistor I1 0.72 A; I 2 1.03 A; I 1.75 A V 6.90 V P 3.68 W The wire has a length 100 cm and the emf of the cell is 6 V ,Determine the balance length L = 50 cm If the cell is replaced with another cell, and the new balance is achieved at 60 cm, determine the e.m.f of the cell. e.m.f. = 6.2 V A 6Ω resistor is connected to the circuit as shown above, Determine 1. New balance length 2. Internal resistance of the cell