Electricity terms

Question 1

ohms law

Answer 1

for a fixed resistor at constant temperature, the current through a resistor is directly proportional to the p.d. across it (V=IR)

Question 2

current

Answer 2

the rate of flow of charge (I=Q/T)

Question 3

potential difference

Answer 3

energy transferred per unit charge (V=W/Q)

Question 4

power

Answer 4

rate of transfer of energy

Question 5

SERIES circuits

Answer 5

• It = I1= I2= I3
• Vt= V1+ V2+ V3 (in proportion with size of resistors)
• Rt= R1 +R2 +R3
• 1/Gt = 1/G1 + 1/G2 + 1/G3

Question 6

PARRALEL circuits

Answer 6

• It= I1+ I2+ I3
• Vt= V1= V2= V3
• 1/Rt = 1/R1 + 1/R2 + 1/R3 (overall resistance from a parallel circuit is always less than the smallest resistor)
• Gt= G1 +G2 +G3

Question 7

terminal potential difference

Answer 7

the p.d. across the load resistors (all the parts of the circuit external to the power supply)

Question 8

potential divider circuit

Answer 8

2 or more resistors in a series used to split the voltage provided from a power supply.

Question 9

semi conductors

Answer 9

a material whose electrical properties depend on external conditions or by adding impurities

Question 10

how do NTC’s work? (thermistor)

(I on y axis, p.d. on X) - mirrored S shape

Answer 10

as heat increases, energy supplied increases meaning outer electrons from semi-conductor have enough energy to escape, which carries the current, decreasing the resistance.

Question 11

how do PTC’s work? (filament light)

(I on y axis, p.d. on X) - S shape

Answer 11

does not obey Ohm’s Law (it is not a straight line) more current= hotter = atoms vibrate faster increasing collisions with electrons = increased resistance

Question 12

how does an LDR work?

Answer 12

semi conductor. Increase in light = more electrons carrying current = increasing current = reduced resistance, little light = less electrons carrying current = reducing current = increased resistance