Electronics

Question 1

Explain the role of valence electrons in the conductivity of metallic conductor. How do these electrons contribute to the flow of electric current (3)

Answer 1

-valence electrons are electrons in the outermost shell of an atom in a metallic conductor
-electrons in the outermost shell are loosely held and can move freely
-the free movement of electrons are responsible for the electric current

Question 2

Elaborate on the concept of a metallic lattice structure, how does the arrangement of positive ions and the movement of valence electrons contribute to the properties of metals such as conductivity and thermal conductivity (3)

Answer 2

-in metal lattice the atoms are arranged in a regular repeating pattern throughout the material
-the sea of electrons move freely throughout the entire lattice which makes them a good conductor
-when heat is applied the valence electrons gain energy and transfer it to neighboring particles which makes it a good heat conductor

Question 3

Define drift velocity (2)

Answer 3

-it is the average speed at which charged particles such as electrons
-move through a wire when an electric current flows

Question 4

What direction do electron flow in a circuit (1)

Answer 4

-from negative to positive

Question 5

What is the direction of conventional current in a circuit (1)

Answer 5

Positive terminal to negative

Question 6

Conductors have 10^29 free electrons

Insulator has 10^9 free electrons

Semiconductors have 10^19 free electrons

Explain why these numbers affect conductivity of a material (2)

Answer 6

-conductivity is a measure of how easily electric charge carried by electrons can flow through a material
-the higher the number of free electrons the better the material conducts electricity

Question 7

Define current (2)

Answer 7

-a measure of the rate of flow of charge

Charge/ time

Question 8

What is the equation of current (1)

Answer 8

= number of free electrons x area x drift velocity x charge on moving electron

Question 9

What is the transferred energy concept (1)

Answer 9

-the energy gained by the electrons (and lost in the rest of the circuit)

Question 10

Define potential voltage (2)

Answer 10

-is a measure of electric potential charge per unit charge in an electric circuit

Energy transferred/charge

Question 11

State the formula for the amount of work it takes to move a charge (2)

Answer 11

W = charge x volatage

And

W = current x potential difference x time

Question 12

State the formula for ohms law (1)

Answer 12

Voltage = current x resistance

Question 13

Define resistivity (2)

Answer 13

-is a property of a material that quantifies its ability to resist the flow of electric current

Resistance = (resistivity x length) / area

Question 14

State the formula for potential energy (1)

Answer 14

= (change in charge) x voltage

Question 15

State the formula for power (4)

Answer 15

Power = current x voltage

= Potential energy / change in time

= current ^2 x resistance

=voltage^2 / resistance

Question 16

How to find resistance for resistors in a series (1)

Answer 16

R1 + R2 + …..

Question 17

How is the current and voltage in series (2)

Answer 17

-current remains the same throughout the circuit in series
-the voltage across the circuit is equal to the sum of the individual voltages
V total = V1 + V2 + V3 …

Question 18

How is the resistance for resistors calculated in parallel circuit (1)

Answer 18

1/R = 1/R1 + 1/R2 + …

Question 19

How is the current and voltage in parallel circuit (2)

Answer 19

-the total current entering the parallel branches is equal to the sum of the current through each brand
I total = I1 + I2 ..

-the voltage is the same throughout the circuit

Question 20

State the Kirchhoff’s junction rule (1)

Answer 20

• at any junction the current entering the junction must equal the current leaving it

Question 21

State the Kirchhoff’s loop rule (1)

Answer 21

• the sum of the potential differences around a closed loop must be zero

Question 22

What is an ammeter (1)

Answer 22

It is a device used for measuring current

Question 23

Should an ammeter have low or high resistance and why (2)

Answer 23

-low resistance
-to ensure accurate results and to mimimise any impact on the circuit being measured

Question 24

What is a voltmeter (1)

Answer 24

• measured the potential drop between 2 points in a circuit

Question 25

Why is a voltmeter connected in parallel (2)

Answer 25

-in order to minimize the effect on the circuit
-it should have great resistance as possible

Question 26

Why should voltmeter have high resistance (1)

Answer 26

-to ensure accurate voltage measurement