Physics Finals

• in an open circuit, there are two opposing electric fields, which eventually cancels each other out, making net charge flow and current zero
• EMF is the influence that makes current flow from the lower potential to higher potential
• EMF brings charges back to the higher potential
• EMF measures the influence of the inside of the source
• potential difference refers to the charge of the battery in the wire or outside the source
• when the charge goes through the battery again, it becomes zero
• voltmeters are placed parallel to the circuit
• ammeters are placed series to the circuit
• electric potential is the potential energy for a charge
• terminal voltage is the electric potential from one end of a battery to another end
• conventional current is the flow of positive chatges
• potential rise is the rise of the charge from the bottom of the circuit to the top
• potential drop is caused by resistors
• power is the product of the voltage and current across one circuit element
• we need a non-electrostatic force stronger than the emf for the current to go out of the positive end, since flow tends to flow from positive to negative
• for power input to a source, work is being done ON the agent that causes the nonelctrostatic force in the upper source
• as charge passes through the circuit element, the electric field does work on the chatge.
• in a source of emf, additional work is done by the force F(n)
• resistors can limit or divide current or reduce or divide a voltage
• for resistors in parallel, each resistor provides an alternative path between the points
• Gustav Robert Kirchhoff was a German physicist
• a junction is a point in a circuit where three or more conductors meet
• a loop is any closed conducting path
• Kirchhoff’s Junction Rule AKA Kirchhoff’s Current Law
• KCL: the sum of the currents into any junction is equal to zero
• Kirchhoff’s Loop Rule AKA Kirchhoff’s Voltage Law
• KVL states that the sum of the potential differences or voltages around any loop is equal to zero
• KCL states that as much current flows into a junction is as much that flows out
• no charge can accumulate at a junction, so the total charge entering a junction per unit time must be equal to the total charge leaving the junction
• KVL is a statement that the electrostatic force is conservative
• travel is the direction that we imagine going around the loop, which is not necessarily the direction of the current
• positive IR = opposite to current
• positive emf: travel from negative to positive
• V(ab) is the potential of A with respect to B
• V(ab): B to A
• dielectric:

  1. it solves the mechanical problem of maintaining two large metal sheets at a very small separation without actual contact
  2. using it increases the maximum possible potential difference between capacitor plates
  3. the capacitance of a capacitor of given dimensions is greater when there is a dielectric material between the plates than when there is vacuum
• dielectric breakdown: the passing through of charges from one conductor to another through an empty space; leak
• capacitor: a device that stores and releases electric potential energy
• capacitance: ratio of the charge of each conductor to the potential difference between the conductor
• dielectric constant (K): a property of a body that allows capacitance and voltage to change