Circuits

Question 1

Kirchoff Laws

Answer 1

1. conservation of current, All charge entering a junction equals all charge leaving said junction
2. Conservation of energy, All potential drops in a circuit equals sum of all emfs inside it

Question 2

Derivations for Resistance in parallel

Question 3

Derivations for Resistance in series

Question 4

Power & Work in circuits

Answer 4

P = IV
w = IVt

Question 5

Ohmic conductor I:V graph

Question 6

Fil bulb I:V graph

Question 7

Thermistor I:V graph

Question 8

Diode I:V graph

Question 9

Potential dividers ratio & Vout equations

Answer 9

Vout = Vin(R1/RT)

V1/V2 = R1/R2

Question 10

LDR

Answer 10

As light intensity increases, Resistance decreases

LDR does opposite to intensity with resistance

Question 11

Emf definition

Answer 11

ammount of chemical energy converted to electrical energy per coulomb of charge (when a charge passes through a power supply)

Question 12

Thermistor

Answer 12

As Temp increases, Resistance Decreases

Question 13

PTC 6 Marker

Answer 13

PTC have ionic lattice and fixed number of free conduction electrons so good conductors at all temps

Temp increases, amplitude of lattice osciallations increases so impedes the flow of electrons v decreases

So less current for same PD therefore Resistance increases with temp

Question 14

NTC 6 marker

(Same argument for LDR - instead of temp its light energy)

Answer 14

Mostly atomic lattice, so very few conduction electrons, conduct poorly at low temp.

At temp increases, amplitude does increase but energy is provided to outer shell electrons to liberate them and make them into free charge carriers, n increases

So greater current for same PD, Resistance decreases for a rise in temp