150 likes | 523 Views
EMF and Terminal Voltage. EMF and Terminal Voltage. Terminal voltage = EMF - Ir. Some of the energy of the cell is used to drive current through the cell. If battery is being charged:. V T = emf + Ir. Cells in Series. Connect a positive to a negative. -. +. -. +. Advantage: EMFs sum.
E N D
EMF and Terminal Voltage Terminal voltage = EMF - Ir Some of the energy of the cell is used to drive current through the cell
If battery is being charged: VT = emf + Ir
Cells in Series Connect a positive to a negative - + - + Advantage: EMFs sum Disadvantage: internal resistance of cells sum
Cells in Parallel Connect positive to positive and negative to negative - - + + Advantages: total internal resistance of cells becomes less; each cell provides current, last longer Disadvantage: does not increase EMF
Automobile Battery – 12 V Jump start - Connect + to +; - to – maintain 12 V
Cells in Series Total resistance: Total EMF: Total current: Terminal Voltage: 40 Ω 12.0 V 0.30 A 6.0 V
20 Ω Cells in Parallel Total resistance: Total EMF: Total current: Terminal Voltage: 25 Ω 6.0 V 0.24 A 4.8 V
Circuit with Short Circuit Switches closed: none: S1: S2: S1 & S2:
R (Ω) V(V) I (A) 0.75 0.75 48 16 36 36 1 2 3 T 12 48 1.33 2.08 23.04 48
I1: I2: I4: V2: V3: V4: 0.03 A R1: R4: 6.0 V 66.7 Ω 0.03 A 8.0 V 57.1 Ω 0.07 A 4.0 V