# Topic 3.2-Complete Electrical Circuits Flashcards Preview

## *Edexcel A-Level Physics* > Topic 3.2-Complete Electrical Circuits > Flashcards

Flashcards in Topic 3.2-Complete Electrical Circuits Deck (22)
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1
Q

How does current flow in series and parallel?

A

Series= constant

Parallel= Itotal= I1 + I2 +…

2
Q

How is voltage distributed in series and parallel?

A

Series= Vtotal= V1 + V2 + …

Parallel= Constant for each branch

3
Q

How is resistance distributed in series and parallel?

A

Series= Rtotal= R1 + R2 +…

Parallel= 1/Rtotal= 1/R1 + 1/R2 +…

4
Q

Derive resistance in series:

A

Vtotal= V1 + V2

Vtotal= I x Rtotal

V1= IR1 and V2=IR2

so… IRtotal= IR1 + IR2

Cancel current: Rtotal= R1 + R2

5
Q

Derive resistance in parallel:

A

Itotal= I1 + I2

Itotal= V/Rtotal

I1= V/R1 and I2= V/R2

so… V/Rtotal= V/R1 + V/R2

Cancel voltage: 1/Rtotal= 1/R1 + 1/R2

6
Q

Give the equation for total resistance in parallel:

A

Rtotal= (R1 x R2)/ (R1 + R2)

7
Q

What is Kirchoff’s first law?

A

The sum of the currents leaving a point is the same as the sum of the currents entering that point.

8
Q

What is Kircoff’s second law?

A

Around any closed loop, the sum of the EMFs is equal to the sum of the PDs.

9
Q

What is the potential divider equation?

A

Vout= Vin x R2/ (R1 +R2)

10
Q

What is a potential divider?

A

A sries circuit that produces an output voltage that is a fraction of its input voltage.

11
Q

What are the uses of potential dividers?

A

Anything that requires a variable voltage or a voltage that differs from the input. For example, light activated switches.

12
Q

What is a potentiometer?

A

A variable voltage supply which uses a movable contact ‘wiper’ to move along a fixed length of resistance wire and alter the lengths of each segment, providing a variable voltage.

13
Q

Define terminal p.d:

A

The voltage across the terminals of a battery.

14
Q

Define internal resistance:

A

The resistance of an EMF source. They can be thought of as the flow of current inside the power supply.

15
Q

What is the equation for internal resistance?

A

Vinternal= Ir

16
Q

What are lost volts?

A

The internal p.d of a power source, found using the equation:

Vterminal= Vload = EMF -Ir

17
Q

What is the equation for EMF, considering energy conservation?

A

EMF= Vload + Vinternal

18
Q

What is a short circuit?

A

A circuit where the only significant resistance is the internal resistance.

19
Q

What is the equation for short circuit current?

A

Current= EMF/ Internal resistance

20
Q

Why might a power supply have a high large internal resistance?

A

To avoid supplying too much current, especially in a high voltage supply.

21
Q

What are the 5 equations for power in circuits?

A

Power= energy/ time

Power= work done/ time

Power= current x voltage

Power= current2 x resistance

Power= voltage2 / resistance

22
Q

What is the equation for efficiency (power or energy)?

A

Eff. = useful energy (or power) out / total energy (or power) in