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BellworkMar. 29, 2018
If you double the distance between two charges, does the force increase or decrease?By how much?
Electric Force• Electric force is an action at a distance force• Can be attractive or repulsive
(How was this seen in the lab this week?)
Electric Field Lines• Electric Field Lines: A way to represent the electric field around charges
• Charge:variable (in equations): q (or Q)unit (measured in): Coulombs (C)
Electric Field Strength• Electric field is a vector (what does that mean?)• Measured in Newtons per Coulomb (N/C)
Voltage and Electric P.E.• Voltage is the electric potential unit is the volt (V)
• Electric Potential Energy: energy of a charge due to its location in the electric field – unit is the joule (J)
Drawing Electric Field Lines• Lines start on positive charges and end on negative charges• The number of lines represents the magnitude of the charge (we will use 4 lines for each 1q)• Label the charges (positive or negative)• Field lines cannot cross each other• Field lines either connect to other lines or go out to infinity, NO DEAD END LINES.• Field lines show the electric field between the charges evenly• Density of field lines represents the electric field strength
Conditions for a Circuit• There must be a closed conducting path that extends from the positive terminal to the negative terminal.
• There must be an electric potential difference across the two ends of the circuit.
Voltage Sources• Do work on each charge it encounters
> Example 1) High voltage low current: (Analogous to a high waterfall with only trickle of water flowing)
> Example 2) Low voltage high current: (Analogous to a low waterfall with a gushing river of water flowing )
Circuit as a Water Slide(analogy)
• Voltage source = The water pump• Voltage (voltage difference) = Height of the slide• Positive terminal = Top of the slide• Negative terminal = Bottom of the slide• Current = Rate at which water is flowing• Charge = The water
• Ohm’s Law: V = I . R
• Electric Power: P = I . VV = voltage (measured in volts, V)I = current (measured in amps, A)R = resistance (measured in ohms, Ω)P = power (measured in watts, W)
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