Model ppq answers

Center of gravity

Point in an object where all of its weight appears to act

Determine specific heat capacity of metal

• Use immersion heater to transfer measurable amount of thermal energy

• Connect to power supply, use ammeter and voltmeter, E = IVt

• Measure change in temperature (final - initial)

• c = E/m(change in temp)

Hot water into dish, end at same temperature

• transfer of energy from higher temperature to lower temperature (water to dish)

• By conduction

• temperature of water decreases, temperature of dish increases

• No energy transfer when temperature dish = temperature water

Why metal expands as heated

• Gain energy in kinetic store

• Particles move further apart

Evaporation

• molecules with more energy escape from surface

What causes little diffraction

Gap with large width compared to wavelength

Explain voltmeter reading when light intensity on LDR increases

• resistance decreases

• e.m.f is constant

• Resistance of LDR is smaller proportion of total resistance

• Voltage LDR is smaller proportion of e.m.f

• R1/R2 = V1/V2

What happens in wires of square coil when resistance is alternately increased and decreased

• changing current

• Causes changing magnetic field

• Coil cuts magnetic field / changing magnetic field

• e.m.f induced

Structure of atom

• no. Electron and proton

• No. Neutrons

• Proton & neutron in nucleus, electrons orbit nucleus

Different compositions of atoms

• x has no. more neutrons

• y has no. more protons/electrons

Galaxy

Collection of billions of stars

Observation speed at which that galaxy is moving away

Increased wavelength, amount of redshift

How to determine distance from galaxy

Brightness of supernova

How speed of galaxy and distance from earth are related

• Speed proportional to distance

• Ho = v/d

Age of universe

1/Ho

kWh

energy transferred in one hour at a rate of transfer of 1 kW

methods of conduction

• delocalized electrons - move through metal, carry energy

• lattice vibrations transfer energy to neighboring particles

boiling vs evaporation

• boiling throughout liquid

• boiling fixed temp (boiling point)

compression & rarefraction

• compression - area of great pressure/particles close together

• rarefraction - area of low pressure/particles spread apart.

p.d

work done in moving unit of charge through component of circuit

deter mine direction of motor movement

• magnetic field, current and motion at right angles

split ring commutator & brush

• split ring: coil continues in same direction, reverses current every half turn

• brush: ensure current maintained

nuclear fission

• large unstable nucleus

• neutron hits nucleon

• splits into smaller nuclei, releasing energy.

redshift

• wavelength increases

• as galaxy moves away from earth

• calculates speed galaxy moves away from earth