Electric Fields Questions

 

Particle Physics Questions

 

1.  C

2.  C

 

 

  3.     (a)

	hadron	baryon	lepton
neutron	y	y
proton	y	y
electron			y
neutrino			y

          4 lines correct 2/2: 3 lines correct 1/2: 2 or 1 line correct 0/2 (2)                           2

 

3.  Three from:

a.       Proton turns into a neutron and positron

b.       Positron is released

c.       Up quark turns to down quark

d.       Electron neutrino released

[3]

 

5.       (i)      up down down / udd;                                                                                          1

  (ii)           Q                B                 S
        u   (+)2/3          (+)1/3              0                                               u values (1)
        d    –1/3           (+)1/3              0                                                d values (1)        2

  (iii)  so for neutron     Q = 0
                          B = 1
                          S = 0                                                                                       1

[4]

 

6.       (i)      leptons;                                                                                                             1

(ii)     neutrino / muon / tau(on);                                                                                   1

[2]

7.       lepton: two examples:  electron; (1)
                                    positron; (1)
                                    neutrino; (1) any 2 (2)
                                    (allow muon, tauon)
3 particles including one wrong gets 1 only

          composition: fundamental (- no quark components); (1)

          forces: weak force / interaction; (1)
            electron / positron - (also) electromagnetic / electrostatic force; (1)

          where found: electron - in atom, outside nucleus or in β– decay; (1)

                               positron (rarely) emerging from (high mass) radioisotopes /
                     in β + decay / accelerating-colliding machines; (1)

                               neutrino - travelling in space eg from Sun
                     or emitted (with electron / positron) in beta decay; (1)

          allow ONCE ‘resulting from high energy particle collisions’                                   any 6

[6]

 

 8.      baryon: two examples proton; (1)
                                    neutron; (1)
3 particles quoted, including one wrong gets 1/2 only

          quark composition:    proton         uud; (1)
                                 neutron       udd; (1)

          (aware consists of 3 quarks, unspecified, gets 1/2)

          stability:   proton stable inside (stable) nucleus; (1)
                 proton possible decay / half life = 1032 years when free; (1)
                 allow any half life > 1030 years

                          neutron stable inside (stable) nucleus; (1)

                          neutron half life = 10/15 minutes when free; (1)                                     any 5

[6]

 

9.       neutron is udd / proton is uud; (1)
quarks are: up down strange top bottom charm; (1)
either up / u has Q = (+)2/3, B = (+)1/3;
or down / d has Q = –1/3, B = (+)1/3; (1)

          quarks are fundamental particles; (1)
for every quark there is an antiquark; (1)
antiquarks have opposite values of Q, B and S (compared to quark) (1)
quarks are held together by strong force / gluons (1)
Q, B and S are conserved in (quark) reactions (1) any 2                                                  5

[5]

 

10

THREE FROM:

the strong interaction ✔

has short range OR mention range (less than 5 fm) ✔

attraction up to 5 fm ✔

repulsive (any distance below 1fm) ✔

is zero/negligible beyond 5 fm ✔

only affects hadrons/ baryons and mesons ✔

mediated by gluons/pions ✔

If wrong interaction identified then zero marks

If refer to strong interaction correctly then ignore any subsequent reference to other interactions

 

Latent heat

 

1. Calculate the energy transferred to the surroundings when 50 g of aluminium changes phase from liquid to solid. E = mL_f  E = 0.050 × 398000 = 20 kJ
2. Calculate the energy required to change 2.5 kg of silver at its melting point from solid to liquid. E = mL_f E = 2.5 × 88000 = 220 kJ
3. When a kettle boils a space can be seen between the spout and the so called `cloud of steam'. If your finger were placed in the space a much more serious scald would result than if it were placed in the `cloud of steam'. Explain why, and criticize the expression `cloud of steam'. Steam is a colourless gas which fills the space, what we see is water vapour condensing in the air as it cools.
4. A 1 kW immersion heater takes 225 s to boil away 0.1 kg of water at 100 °C. Show that the specific latent heat of vaporization of water is about 2.1 KJkg^-1  

E =Pt = mL_v  1000 x 225 = 0.1L_v   Lv= 225000/0.1 = 2.25 kJkg^-1

5. Describe why the specific latent heat of vaporisation is normally greater than the specific latent heat of fusion for a particular substance. There is a greater change in internal energy changing phase from liquid to gas than from solid to liquid
6. A mixture of ice and water at 0 °C contains 0.060 kg of ice. A 750 W immersion heater takes 26.8 s to melt all the ice. Show that the value for the specific latent heat of fusion of ice is approximately 3.4 x 10⁵ Jkg^-1.

E =Pt = mL_v  750 x 26.8 = 0.060L_v   Lv= 20100/0.060 = 3.35 x 10⁵ Jkg^-1

Temperature Scales

 

Solids Liquids and Gases