Module 2: Series DC Circuits
RecapRecap Do you still recall these?
Recap What are electric circuit components? Does the current flow in an open or close circuit? Give examples of five output devices
Outlines Series circuit Current in a series circuit Resistance in a series circuit Voltage in a series circuit – Kirchhoff’s Voltage Law – Voltage divider circuit Power in a series circuit Variable resistor Trouble Shooting series circuit
Technical words and units Voltage across R Voltage drop across R Current through R Power dissipated in R Voltage: v Current: A Resistance: Ω Power: W
Series circuit connecting of components end to end in a circuit to provide a single path for the current. How many paths you have for the current?
Do you think it only applies for resistors?
It is common to connect input devices in series (power supplies) It is not common to connect loads in series. Why ??
Applications of series circuits Search the web for real examples of series circuit.
Exercise 1 page 4 Using wires, connect all of the cells in series to create a 6V battery source. Then connect all of the lamps in series with the battery.
Solution of Exercise 1
What is the total voltage ?
Is this correct ?
Current in a Series Circuit A series circuit has only path for current to travel The current through a series circuit is the same I T = I 1 = I 2 = I 3
Resistance in a Series Circuit Resistance is the opposition to current flow T = R4
Example1 Calculate the total resistance of the circuit Can be drawn as:
RTRT
How many path exist for the current in the series circuit? What happen to the current in the series circuit? What happen to the resistance in the series circuit?
Ohm’s Law = × Where V = voltage (Volts) I = current (Amps) R = resistance (Ohms)
Example Find the current.
Voltage in a Series Circuit The total voltage supplied by the power supply is divide among the loads
Kirchhoff’s Voltage Law total voltage in a series circuit is equal to the sum of the individual voltage drops in the circuit. T= …
Voltage Divider V1 = [R1/(R1+R2)]*V V2 = [R2/(R1+R2)]*V V: Source voltage
Variable Voltage Divider Potentiometer is a variable resistor with three terminals.
Power is a series circuit Power’ is the measure of the energy consumed by a circuit. Unit: Watt = × = 2 × P = V 2 /R T = …
Important Notes The resistance of the open component is huge The resistance of the short component is zero Open switch has huge resistance Close switch has zero resistance
Problems in a series circuit Problems in series circuits A component is open a component’s value will change over a period of time A component is shorted
A component is open Lamp 3 is open The current is zero All the lamps are OFF, all voltage is dropped across Lamp3 V1 = V3 = zero
A component is shorted Lamp 2 is short The current is not zero Lamp2 is OFF, Lamp 1 and 3 ON V2 = Zero V1 = V3 = 9/2 volts
LAB ACTIVITY 3LAB ACTIVITY 3
LAB ACTIVITY 3: Safety instructions Be quite Don’t switch ON the power supply till the teacher check the circuit for you Take the measurements quickly because the resistors will get very hot
LAB ACTIVITY 3, Stage-1: R1 = 820Ω R2 = 470Ω V2calculated = V2measured =
LAB ACTIVITY 3, Stage-2: V2VR1R2V2 measured 39R2/2R2 59(5/4)R1R2
LAB ACTIVITY 3, Stage-3:
Conclusion Current in series circuit Resistance in the series circuit Voltage in the series circuit Power in the series circuit Kirchhoff voltage law