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CfE Higher Physics

Learn about electric fields, forces on charges, potential difference, and kinetic energy in an electric field. Practice calculations and concepts.

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CfE Higher Physics

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  1. CfE Higher Physics Unit 2 Particles and Waves Electric Fields and Movements of Charge

  2. Learning Intentions • To be able to state that, in an electric field, an electric charge experiences a force. • State that an electric field applied to a conductor causes the free electric charges in it to move.

  3. Electric Fields An electric field is a region of space in which charged particles experience a force. When an electric field is applied to a conductor the free electric charges are caused to move. Electric fields can be represented by field lines. These lines show the direction in which a positive charge experiences the force. The closer together the lines the stronger the force.

  4. - + - + - + - + - + - + Field Patterns Positive point charge Negative point charge Positive and negative point charges Parallel charged plates

  5. Electric Fields Charges experience a FORCE in electric fields. When an electric field is applied to a conductor the free electric charges are caused to move. Electric fields can be represented by field lines. These lines show the direction in which a positive charge experiences the force. The closer together the lines the stronger the force.

  6. - + - + - + - + - + - + Field Patterns Positive point charge Negative point charge Positive and negative point charges Parallel charged plates

  7. Success criteria • To be able to state that, in an electric field, an electric charge experiences a force. • State that an electric field applied to a conductor causes the free electric charges in it to move.

  8. Learning Intentions • State that work, W, is done when a charge, Q, is moved in an electric field. • State that the potential difference (V) between two points is a measure of the work done in moving one coulomb of charge between the two points • State that if one joule of work is done moving one coulomb of charge between two points, the potential difference between the points is one volt. • State the relationship V = W/Q. • Carry out calculations involving the relationship V = W/Q • Calculate the speed of a charged particle accelerated in an electric field using the relationship QV = ½ mv2.

  9. Ew V = W = QV Q Potential Difference When a charged particle is moved in an electric field work is done. Charges can accelerate in electric fields. The potential difference (p.d.) between two points is a measure of the work done in moving one coulomb of charge between the two points. The SI unit of potential difference is the volt, V.

  10. W V = Q Voltage definition From the equation: we are able to state the definition of 1 volt: When 1 Joule of work is done in moving a 1 Coloumb of charge between two points there in a potential difference of 1 Volt. Charges can accelerate in an electric field. V= voltage (V) W = work done (J) Q = charge (C) W = QV

  11. Potential difference and kinetic energy

  12. Potential difference and EK

  13. Worked Example A particle with a mass of 3.6 x10-6 kg and a charge of 4.8 x10-6 C is accelerated from rest through a potential difference of 20 kV. Calculate the final velocity of the particle. Work done = Increase in kinetic energy QV = ½mv2 4.8 x10-6 x 20,000 = ½ x 3.6 x10-6 v2 v2 = 5.33 x104 v = 231 ms-1

  14. The Electron Volt • Sometimes we measure energy of charges in electron volts, eV. • 1eV = 1.6x10-19 C x 1V = 1.6x10-19 J • (Using E=QV) • The small e simply stands for the charge of an electron. When you see a small “e” this is what it will mean!

  15. Learning Intentions • State that work, W, is done when a charge, Q, is moved in an electric field. • State that the potential difference (V) between two points is a measure of the work done in moving one coulomb of charge between the two points • State that if one joule of work is done moving one coulomb of charge between two points, the potential difference between the points is one volt. • State the relationship V = W/Q. • Carry out calculations involving the relationship V = W/Q • Calculate the speed of a charged particle accelerated in an electric field using the relationship QV = ½ mv2.

  16. Quiz – No notes! • Name a lepton • Name a particle made up of 3 quarks • What’s another name for a particle made up of 3 quarks? • What’s a meson made up of? • Name a boson. • Name the force associated with this boson? • What forces in the nucleus are balanced? • What’s the defintion of 1 volt? • What’s the equation for work done in an electric field? • What equation would you use to work out the velocity of a particle as it travels through an electric field?

  17. Answers

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