5.3 - Circuits & The Potential Divider

Question 1

What is the combined resistance of resistors in series?

Answer 1

RT = R1 + R2 + R3…

Question 2

What is the combined resistance of resistors in parallel?

Answer 2

1/RT = 1/R1 + 1/R2 + 1/R3…

Question 3

What is the current of the components in a series circuit?

Answer 3

They are all the same current.

Question 4

What is the current of the components in a parallel circuit?

Answer 4

Depends on the branch.
The amount of current in each depends on RT in the branch.
IT into junction = IT out of junction

Question 5

What is Kirchhoff’s 1st law?

Answer 5

The total current that enters a junction is equal to the total current that leaves the junction.

Question 6

What is the voltage flowing through components in a series circuit?

Answer 6

The e.m.f of the power supply is shared amongst all the components in different amounts depending on their resistance.

Question 7

What is the voltage flowing through components in a parallel circuit?

Answer 7

The voltage of all the components in each branch is equal to the e.m.f of the power supply.

Question 8

Is charge conserved in a circuit?

Answer 8

It is never used up or lost in a circuit so yes.

Question 9

What is a junction?

Answer 9

A point where at least 3 circuit paths meet.

Question 10

What is a branch.

Answer 10

A path connecting 2 junctions.

Question 11

What is Kirchhoff’s first law in numbers?

Answer 11

I = I1 + I2 + I3

Question 12

What is Kirchhoff’s 2nd law?

Answer 12

The total e.m.f in a closed circuit equals the sum of the potential differences across each component.

Question 13

What are the equations for power?

Answer 13

P = E/t
P = IV
P = I²R
P = V²/R

Question 14

What can the formula for energy be written as?

Answer 14

E = VIt
(voltage, current, time)

Question 15

What are potential dividers?

Answer 15

A circuit with several resistors in series connected across a voltage source, used to produce a required fraction of the source potential difference, which remains constant.

Question 16

What are the 2 main purposes of potential dividers?

Answer 16

• To provide a variable potential difference to enable a specific potential difference to be chosen
• To split the potential difference of a power source between 2 or more components

Question 18

What is the potential divider equation?

Answer 18

Vout = (R2 / R1 + R2)Vin

Question 19

What is an LDR?

Answer 19

A sensory resistor (like a thermistor) which stands for light dependent resistor.

Question 20

What is the symbol for a LDR?

Answer 20

A rectangle with 2 arrows pointing at it.

Question 21

With LDR, what is the relationship between light intensity and resistance?

Answer 21

The higher the light intensity, the lower the resistance.
The lower the light intensity, the higher the resistance.

Question 22

What is the relationship between Vout from a resistor in a potential divider circuit?

Answer 22

The potential difference is proportional to its resistance.
LDR/thermistor’s resistance decreases, p.d decreases (vice verse)