12 Electric current

Question 1

charge carriers

Answer 1

charged particles that move through a substance when a pd is applied across it

Question 2

potential difference

Answer 2

work done or energy transfer per unit charge between two points when charge moves from one point to another
V = W/Q

Question 3

resistance

Answer 3

pd / current

Question 4

ohm’s law

Answer 4

the pd across a metallic conductor is proportional to the current, provided the physical conditions do not change

Question 5

resistivity

Answer 5

resistance per unit length x area of cross-section

Question 6

superconductor

Answer 6

a material that has zero electrical resistance

Question 7

critical temperature a superconducting material

Answer 7

temperature at and below which its resistively is zero

Question 8

light-dependent resistor

Answer 8

resistor which is designed to have a resistance that changes with light intensity

Question 9

postive temperature coefficient

Answer 9

the resistance of a metal increases when its temperature is increased

Question 10

negative temperature coefficient

Answer 10

the resistance of a semiconductor increases when its temperature is increased

Question 11

current equation

Answer 11

∆Q = I∆t

Question 12

emf of a source of electricity

Answer 12

as the electrical energy produced per unit charge passing through the source

Question 13

work done

Answer 13

W=IV∆t

Question 14

electrical power

Answer 14

P=IV

Question 15

resistance equation

Answer 15

R=V/I

Question 16

resistivity equation

Answer 16

p = RA /L

Question 17

diode

Answer 17

only let the current go one way (0.6v)

Question 18

electric current

Answer 18

rate of flow of charge

I= Q/t

Question 19

potential difference

Answer 19

work done per unit charge

V=W/Q

Question 20

unless stated in questions ammeters and voltmeters should be treated as ideal

Answer 20

zero and infinite resistance respectively

Question 21

negative coefficient

Answer 21

A negative coefficient for a material means that its resistance decreases with an increase in temperature. Semiconductor materials (carbon, silicon, germanium) typically have negative temperature coefficients of resistance.