Exam 1 Review Phys 222 Supplemental Instruction Do you know all the - - PowerPoint PPT Presentation

Good Luck! Exam 1 Review

Phys 222 – Supplemental Instruction

Do you know all the following?

• Electric Charge
• Coulomb’s law
• Charged objects’ behavior
• Conductors, Insulators, Polarization
• Electric Charge Interaction
• Electric field, field lines
• Dipoles, dipole moment
• Flux
• Integral Representation
• Gaussian Representation
• Applying Gaussian surfaces to objects

• Electric Potential
• (vs) Electric Potential Energy
• Equipotential Diagrams
• Calculating potential at various points
• Movement of charge in the presence of a potential.
• Relation to other types of energy

• Capacitance
• How various changes affect capacitance
• What are their uses
• Connections in circuits
• Parallel vs series
• Equivalent capacitance
• Dielectric additions
• Current
• Relation to other concepts
• Resistance
• Connections, much like capacitors

Here we go!

LOTS OF TEST PROBLEMS WITH TIPS SPRINKLED IN

Electric Force Electric Field Electric Potential Energy Electric Potential Difference (voltage)

Divide by q

Field descriptions: Do not depend on recipient particle/charge. Recipient charge -- q Forces and energy: Depend on recipient and emanating charge. Emanating charge -- Q

Field lines!

 Electric field lines go from + to -  Electric field lines end at negative charges.  Line density indicates field strength

Dipoles

 𝒒 = |𝑅|𝒆

(dipole moment)

 !! Notice: Dipole moment points from negative

to positive….opposite of the direction E points

Dipole Moment and Torque

 𝝊 = 𝒒×𝑭

 Know right hand rule for cross products!

This will help you eliminate wrong choices

 Note that E is not the E produced by dipole. E is

external

 Torque minimums and maximums

 Max when p perpendicular to E

 U = -p ⋅ E

Steps in solving GL Problems

 Draw a picture.

 Pick a good Gaussian surface. Symmetry!

 Write expression of integral flux notation. (if E parallel to A then, EA)  Write expression for Gauss’s Law involving enclosed charge.  Set the expressions equal and eliminate variables to solve.

Relating Charge (Q) to field (E)

Is the charge distribution discrete (set

• f charges)?

Use Coulomb's law on each and add results using vector addition. Is there symmetry? Use Gauss’s law to relate charge enclosed to the field at any point. Was it solved in class? Use a formula such as for an infinite plane

• r ring of

charge. Solve for the relation by setting up an integral version of Coulomb’s law with dq and dr

No Yes No No Yes Yes

Cylinder with charge 5C

Capacitance and Energy

 𝑉 =

1 2 𝐷𝑊2 = 𝑅2 2𝐷 = 1 2 𝑅𝑊

 Wait, why are there three equations?

 If asked to calculate U, just use the one that has known variables  If asked what happens to U when you double, half, etc.

 If the capacitors are stand alone, use Q^2 equation  If the capacitors are connected to constant voltage use V^2

equation

Combining components

Capacitors Resistors Addition T = X1 + X2 +… Inverse Addition 1/T = 1/X1 + 1/X2 +… Addition T = X1 + X2 +… Inverse Addition 1/T = 1/X1 + 1/X2 +…

Parallel Series

Hodgepodge

OF RELEVANT QUESTIONS