Electricity

Question 1

What is Current?

Answer 1

the rate of flow of charge

Question 2

What is a Coulomb?

Answer 2

the amount of charge that passes in 1second when the current is 1amp.

Question 3

What is potential difference?

Answer 3

the energy per unit charge

Question 4

What is Ohm’s Law?

Answer 4

The current through an ohmic conductor is directly proportional to the potential difference across it, provided the temperature is constant

Question 5

What does the I/V graph look like for a metallic conductor?

Answer 5

a straight line, through the origin

Question 6

What does the I/V graph look like for a filament lamp?

Answer 6

S curve, going through the origin

Question 7

What does the I/V graph look like for a thermistor?

Answer 7

sinh(x) graph

Question 8

What are semiconductors used for?

Answer 8

they are used in sensors

Question 9

What is a thermistor?

Answer 9

a resistor with a resistance that depends on its temperature

Question 10

What is the relationship between light intensity and resistance for an LDR?

Answer 10

the greater the intensity of light, the lower the resistance

Question 11

what is the functions of a diode?

Answer 11

only lets current flow in one direction

Question 12

What is the name of the direction in which a diode allows current?

Answer 12

forward bias

Question 13

What is resistivity?

Answer 13

the resistance of a 1m length with 1m^2 cross sectional area

Question 14

what is the equation for resistivity?

Answer 14

p= (RA)/L

Question 15

what does resistivity depend on?

Answer 15

-Length
-Area
-Resistivity

Question 16

What is the key feature of a superconductor?

Answer 16

it has zero resistance

Question 17

what is the problem with superconductors?

Answer 17

-needs to be kept at very cold temperatures
-hard and expensive to operate due to cold temperatures

Question 18

What are the uses of superconductors?

Answer 18

-Power cables
- Strong electromagnets in medical equipment
-fast electric circuits

Question 19

What is Power?

Answer 19

the rate of transfer of energy

Question 20

Where does resistance come from?

Answer 20

electrons colliding with atoms

Question 21

What is Internal Resistance?

Answer 21

resistance of the battery

Question 22

What is Emf?

Answer 22

• Electromotive force
• the amount of electrical energy the battery produces for each coulomb of charge

Question 23

what is terminal p.d?

Answer 23

the voltage across the cell when there is a current. i.e when there is internal resistance.

Question 24

What is the equation for Emf?

Answer 24

E= V + Ir

Question 25

what is the gradient and y-intercept of the V/I graph?

Answer 25

gradient: negative internal resistance
y-intercept: emf

Question 26

What is Kirchhoff’s 1st Law?

Answer 26

the total current entering a junction = the total current leaving it

Question 27

What is Kirchhoff’s 2nd Law?

Answer 27

The total emf around series circuit = the sum of the p.d.s across each component

Question 28

What is a potential divider?

Answer 28

a circuit with a voltage source and a couple of resistors in series and the potential difference is divided in the ratio of the resistances

Question 29

What is AC?

Answer 29

alternating current, current that changes with time