Circuits

Question 1

What is current?

Answer 1

the rate of flow of charged particles

Question 2

what is ohms law?

Answer 2

V is directly proportional to I when T is constant

Question 3

what is kirchhoff’s first law?

Answer 3

the total I flowing into a junction = to the total charge flowing out of the junction

Question 4

what is kirchoffs second law?

Answer 4

in any closed loop the directed sum of p.d = 0

Question 5

what is the conservation of energy?

Answer 5

energy cannot be created or destroyed, only transferred, so in a closed system energy stays constant

Question 6

How is I distributed in series and parallel?

Answer 6

in series I is the same everywhere, in parallel the sum of each branch = total I

Question 7

How is p.d distributed in series and parallel?

Answer 7

In a series circuit p.d is the sum of all the p.ds . In parallel the p.d is equal in each branch

Question 8

How is resistance (R) distributed in series and parallel?

Answer 8

In series RT=R1+R2+R3, In parallel, 1/RT= 1/R1+1/R2+1/R3

Question 9

what is a potential divider?

Answer 9

A potential divider is used to produce a required fraction of the source p.d.

Question 10

How can you make a potential vary?

Answer 10

By using a variable resistor

Question 11

what is the relationship between light intensity and LDR resistance?

Answer 11

As light intensity increases, LDR resistance decreases. This is due to the photoelectric effect. More electrons are released with the light intensity increase, therefore the amount of charge carriers increases, meaning the R decreases

Question 12

what is internal resistance?

Answer 12

the resistance within the battery, the atoms colliding .

Question 13

what is electromotive force (emf)?

Answer 13

the energy transferred per coulomb of charge that passes through it

Question 14

What does increases in temperature do to a lattice?

Answer 14

As the T increases, the energy of the particles increase. Therefore, the intensity of the vibrations increase. When the intensity increases the resistance of the material also increases due to the electrons not being able to pass through as easily without colliding.

Question 15

what is the relationship between temperature and resistance in a metal or semiconductor?

Answer 15

As the temperature increases the atoms gain energy which liberates some electrons (thermionic emission) which increases the number of charge carriers, therefore R will decrease

Question 16

what is the relationship between T and R in metallic conductors?

Answer 16

R increases with T because the electrons are not liberated quickly enough.

Question 17

What are valence and conduction bands?

Answer 17

The valence band is full of unexcited electrons, when the electrons gain energy, they excite and jump into the conduction band.
The valence band is simply the outermost electron orbital.
The band gap is the gap between the valence and conduction band, the highest energy state in the valence band compared to the lowest energy state in the conduction band is the energy needed to move from valence to conduction