Electricity

Question 1

How do u find the peak voltage using an oscilloscope

Answer 1

Y gain setting x number of divisions

Question 2

How do u calculate the period of waves using an oscilloscope

Answer 2

Time base setting x number of divisions

Question 3

Current and voltage in a series circuit

Answer 3

Current is equal all over
Voltage adds up

Question 4

Current and voltage in a parallel circuit

Answer 4

Current adds up
Voltage is equal all over

Question 5

If u increase the resistance…

Answer 5

Current decreases

Question 6

How can the voltage across a Wheatstone bridge be determined…

Answer 6

By calculating the voltage across each of the bottom resistors in the potential dividers and then calculating the difference between these two voltages.

Question 7

What voltage is measured in an open circuit

Answer 7

EMF

Question 8

Terminal potential difference

Answer 8

The energy per unit change available at the terminals of the electrical source

Question 9

What is a capacitor?

Answer 9

An electrical component that stores electrical charge

Question 10

Capactiance

Answer 10

Charged stored per volt

Question 11

Farad

Answer 11

One Colomb of charge per volt of potential difference

Question 12

Increasing the capacitance

Answer 12

Increases the time taken for the capacitor to charge/discharge

Question 13

Increasing the resistance of a capacitor

Answer 13

Increases the time for a capacitor to charge/discharge

Question 14

Conductors have…

Answer 14

Many free electrons which can easily move through the materials

Question 15

Insulators have…

Answer 15

Very few free electrons

Question 16

Semiconductors are…

Answer 16

Insulators are pure won’t conduct but they will conduct when an impurity is added or when exposed to heat/light

Question 17

Band theory for a conductor

Answer 17

The highest occupied band is not completely full so electrons can move and therefore conduct. (Conduction band) the valence band is full so electrons can’t move. At room temp the valence band overlaps the conduction band this assists conductions

Question 18

Band theory for an insulator

Answer 18

Valence band is full so no movement therefore no conduction. The gap between the valence and conduction band is large so there is not enough energy available to move the electrons from the valence to the conduction band. Therefore there is no conduction in insulators.

Question 19

Band theory for a semiconductor

Answer 19

The gap between the valence and conduction band is small, so at room temp there is sufficient energy to move some electrons from the valence to the conduction bands, therefore some conduction takes place. The electrons also leave holes I. The valence band which allows for further conduction to take place.

Question 20

(Conductivity) Increasing the temperature….

Answer 20

Increases conductivity in a semiconductor

Question 21

Doping is when…

Answer 21

The electrical properties of semiconductors are altered

Question 22

N-type semiconductor…

Answer 22

Provides extra electrons. The extra electrons occupy energy levels close to the conduction band and therefore easily excited into the conduction band. Majority of carriers are negative

Question 23

P-type semiconductor

Answer 23

Has less electrons. Gaps at energy levels just above the valence band, therefore they are easily excited into these levels leaving behind holes in the valence band. Majority of carriers are positive.

Question 24

What is a p-n junction?

Answer 24

When two different types of semiconductors are placed in contact with each other

Question 25

Photovoltaic effect

Answer 25

When photons with sufficient energy go into the p-n junction giving the electrons enough energy to move from the valence band to the conduction band, this allows for a current to be drawn

Question 26

What is the Vlost equation

Answer 26

Vlost = Ir

Question 27

That is the equation that connects Vlost Vtpd and E

Answer 27

E= Vtpd + Vlost

Question 28

Using band theory explain how an LED emits light

Answer 28

-Electron moves towards the conduction band of the p-type
-Electrons move from the conduction band to the valence band
-A photon is emitted