ELECTRICITY Electric Current & Potential difference Ohm’s law & Resistance Resistance in series & Parallel Electric power & Heating effects of current
EPISODE 3 Resistance in Series & Parallel
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Q1. If the voltage is increased and the resistance stays the same, current will A B increase decrease C D Stays the same Can’t say
Q1. If the voltage is increased and the resistance stays the same, current will A B increase decrease C D Stays the same Can’t say
Q2. What is resistance? A B The flow of electrons Electric potential difference C D A battery The ability to reduce the flow of electrons
Q2. What is resistance? A B The flow of electrons Electric potential difference C D A battery The ability to reduce the flow of electrons
Q3. What is the Voltage of a circuit that has a resistance of 5 Ω and a current of 2 A? A B 25 V 2.5 V C D 1V 10 V
Q3. What is the Voltage of a circuit that has a resistance of 5 Ω and a current of 2 A? A B 25 V 2.5 V C D 1V 10 V
Consider the Toll Booth
What if 3 toll booths are placed one after the other
What if 3 toll booths are placed one after the other Adding toll booths one after the other increases the traffic
RESISTOR = TOLLBOOTH MORE RESISTANCE
Now consider a circuit with 2 resistors R1 and R2. R1 R2
Current in resaisntodrIs2.R1 and R2 is I1 I1 I2 R2 R1 I V
Is the current through both the resistors same? A B YES NO C No comments
Is the current through both the resistors same? A B YES NO C No comments
WHY??? Is the current through both the resistors same? A B YES NO C No comments
CURRENT = TRAFFIC Amount of traffic is same throughout all the toll
CURRENT = TRAFFIC Amount of traffic is same throughout all the toll Implies current is same throughout all the resistors
Current in R1 = Current in R2 = Current in the circuit I = I1 = I2
V1 V2 A R1 B R2 C I V Let the voltage across R1 be V1 and the voltage across R2 be V2
Is the potential difference across R1 = Potential at A - Potential at B A B YES NO C No comments
Is the potential difference across R1 = Potential at A - Potential at B A B YES NO C No comments
V1 = VA - VB Similarly , V2 = VB - VC
If we add them we get V1 + V2 = VA - VC
If we add them we get V1 + V2 = VA - VC V1 + V2 = V
Current remains constant Voltage gets distributed
Equivalent circuit B I = I1 = I2 V = V1 + V2 A I Re Apply Ohm’s law, I1R1 + I2R2= V q I1R1 + I2R2= IReq R1 + R2= Req V
In series connection, Equivalent resistance is the sum of individual resistances. Req = R1+R2
For 2 resistances I R1 R2 Req = R1 + R2 V For 3 resistances R1 R2 R3 Req = R1 + R2 + R3 IV
For n resistances R1 R2 R3 Rn I V Req = R1 + R2 + R3 …….. + Rn
In series combination equivalent resistance is _______ than individual resistance A B smaller larger C D same Don’t know
In series combination equivalent resistance is _______ than individual resistance A B smaller larger C D same Don’t know
In series combination, resistors/ devices are connected one after the other Current Remains the same. Voltage gets distributed. Equivalent resistance is sum of individual resistance.
What if 3 toll booths are placed parallel to one another?
What if 3 toll booths are placed parallel to one another? This way reduces the traffic
RESISTOR = TOLLBOOTH LESS RESISTANCE
Let’s connect ends of the resistors together. And analyse them
What is the voltage across the resistors?
Potential difference across R1 = Potential at A - Potential at B Similarly V1 = VA - VB V2 = VA - VB
V1 = V2 R1 AB I R2 V V1 = V2 = VA - VB
V1 = V2 R1 AB I R2 V V1 = V2 = V
What will be the current flowing through the resistors?
CURRENT = TRAFFIC Current is different in different toll booths
Voltage remains constant Current gets distributed
V = V1 = V2 I = I1 + I2 Apply Ohm’s Law,
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