2nd PPE Physics Revision

PPE Physics Paper 1 Revision

Investigating Resistance:

R= V/I (Resistance= Potential Difference/ Current)

(Ohm) (Volt) (Amps)

Electric Current flows when Electrons move through a conductor (Metal Wire). Moving Electrons can Collide with Ions within Metal= Difficult for Current to Flow= Resistance

Resistance will Increase if:

1) Length of Wire Increase

2) Thickness of Wire Decrease

Total Resistance in Series= R1+R2

Total Resistance in Parallel= 1/R1+1/R2

Radioactivity:

Why are Atoms Radioactive?

Too many Neutrons= Unstable Nucleus= Emit Radiation- Alpha, Beta, Gamma

Alpha:

When a Nucleus Emits Alph Radiation, it Emits a Helium Nucleus= Emits 2 Neutrons+ 2 Protons

Stopped by Paper

Air Range (Before Hitting)= 5cm (Few cm in Air)

Least Penetrating

Strongly Ionising

Magnetic Field: YES

Aplha Decay: Decrease Mass and Charge of Nucleus

4

   He= Alpha     228          -4     224        4

2                       Th                  Ra   +   a

                    90           -2     88         2

Beta: 

Neutron turns into Proton+ Emits Fast Moving Electron

No Mass= 0 neutrons (Atomic Mass)

Stopped by Aluminum 

Air Range (Before Hitting)= 10 cm

Moderately Ionising

Moderately Penetrating

Magnetic Field: YES

Beta Decay: Increase Charge of Nucleus+ Same Mass+ Neutron turns into Protons

0                 14        0       14         0

  e-                 C                 N   +     e-

-1                6          +1      7          -1

Gamma: Don't Change because it's a way to get Rid of Excess Energy from Nucleus= Don't Change Atomic Mass+ Number

Electromagnetic Wave with Short Wavelength 

Least Ionising

Most Penetrating

Air Range= 10 km

Magnetic Field: No

History of the Atom:

Dalton: 

Thompson: Electrons+ Plum Pudding

Rutherford: Nucleus+ Nuclear Model

Bohr: ELectrons Orbit Round the Nucleus

The Plum Pudding Model:

Thompson: Sphere of Positive charge with Electron dotted Inside like Plums in a pudding. He knew that an atom= Neutral therefore, something in the atom Must be Positive due to his discovery of the Electron.

However, the Plum Pudding was Incorrect because Rutherford's Alpha Scattering experiment showed that it was wrong because they expected the Alpha to pass Straight Throughor some to Slightly Deflect- Positive charge was thought to be Spread out Covering most of the Atom.

Most did go Straight+ some Deflected More than Expected BUT Some Deflected Backwards= Plum Pudding= Incorrect

OBS: Some Deflected + Passed Straight through like Predicted BUT some Deflected Backwards

Why Did Most particles pass Straight Through?

There is Empty Space within an atom- Plum Pudding shows Positive charge…