U2 electricity question

Question 1

Explain why reading on voltmeter is less than 9V when switch is closed

Answer 1

-p.d. is the energy transfer per unit charge
-voltage is dropped across internal resistance
-less voltage is dropped across rest of the circuit

Question 2

The student suggested that if emf of battery is doubled, reading on the voltmeter will double (have thermistor in series)

Answer 2

• increase e.m.f. increase current
  -increase current increase temperature
  -increase temperature resistance of thermistor decreases
  -total potential difference across thermistor decreases, voltmeter increases for the voltmeter reading

Question 3

Resistance of parallel combination vs resistance of single resistor

Answer 3

Resistance of parallel combination is always less than single resistor in parallel with others

Question 4

Explain why intensity of light detected is less than intensity of light transmitted by pollarising filter A.

Answer 4

Light is rotated by a small angle. Only a component of the light is transmitted by filter B

Question 5

Why intensity of light transmitted through polarising filter varies (y=cosx + 1)

Answer 5

Maximum intensity at 0,180,360 as filter is parallel to the light
As filter rotates, intensity changes as only component parallel to the filter is transmitted
Minimum intensity at 90, 270. Filter is perpendicular to the light
Intensity is never zero as light s not completely polarised

Question 6

Describe how to demonstrate the light from the laser pointer is plane polarised

Answer 6

Light directed through one polarising filter
Filter is rotated until no light passes through