Ch 21 sec 2 w 6 and 7 tr 2 Applications_of_Electric_Fields

Electric potential is the electric potential energy per unit charge, commonly referred to as voltage.

Electric potential difference (ΔV):
- Defined as the work (W) needed to move a positive test charge from one point to another, divided by the magnitude of the test charge.
- Also understood as the change in electric potential energy (ΔPE) per unit charge.
- Measured in joules per coulomb (J/C), where 1 J/C = 1 V.
- When the electric potential difference between positions is zero, those positions are at equipotential.

A uniform electric field can be created using two parallel conducting plates (+ and -).
The electric field is consistent between plates except at the edges, directed from positive to negative.
The electric potential is higher near the positively charged plate and lower near the negatively charged plate.
The electric potential difference (ΔV) can be calculated using the formula linking electric field strength, separation distance, and potential difference.

Situation: Two charged parallel plates, 4.0 cm apart, with an electric field of 2400 N/C.
Known: E = 2400 N/C, d = 4.0 cm
Unknown: ΔV and work (W) to move a proton from one plate to another.

Experiment: An oil drop weighing 1.5×10−14 N is suspended between charged plates with potential difference of 450 V (2.4 cm apart).
Known: ΔV = 450 V, Fg = 1.5×10−14 N
Unknown: Charge (q) and number of excess electrons (n) on the oil drop.
The electric force equals gravitational force in a balanced state.

Electrons in conductors repel each other and spread out to minimize potential energy.
Charges rest on the surface of conductors; the electric field is zero inside a closed charged metal container.
The electric field is stronger at sharp points of conductors.

A capacitor stores electrical energy in an electric field.
With a 1-V connection, the potential difference results in a net positive charge (+q) on one plate and an equal negative charge (-q) on the other.
The capacitance (C) is defined in a straight line relation between charge and potential difference in a charge vs. potential graph.
Capacitance is measured in farads (F), where 1 F = 1 C/V.

Situation: Charging a sphere with potential difference of 76.0 V and charge of 3.8×10−4 C.
Known: q = 3.8×10−4 C, ΔV = 76.0 V.
Unknown: Capacitance (C).

Capacitors come in various forms for use in electronics such as computers and televisions.
Capacitance can be adjusted by changing the surface area, distance between plates, or the insulating material used.
Typical capacitance values range from 10 picofarads to 500 microfarads, with specialized memory capacitors having capacitance ranging from 0.5 F to 1.0 F.

Electric potential difference is crucial for understanding the work needed to move charges and capacitor properties.
Vocabulary concerning electric potential is essential for a comprehensive understanding of electric fields.