Electricity Review Questions and Study Guide

Electricity Review Questions and Study Guide

Electricity Review questions and Study guide

Types of problems for Electricity Unit:

Determine electrical forces using Coulombs law. Vector problem(Day 2)

Determine electric field due to charges. Vector problem. (Day 2)

Sketch Field diagram showing field lines and equipotential lines.

Determine current in a wire due to moving charges. Definition of current = charge/time. I=nqAv

Resistance in wires. R = L/A

Ohms Law

Simple Series and Parallel circuits to solve.

Combined Circuit(Day 2)

Kirchoff Laws circuit(Day 2)

Determine electric potential due to charges. Scalar problem.

Relate potential to work.

Relate potential to electric field. Especially between parallel plates.

Too many time consuming problem solving type questions to assess within a 90 min class period. Therefore the Electricity test will be two part. 1/2 for Tues, and 1/2 for Thurs. Topics for the Day 2 portion are the more time consuming problems. All other types of problems will be included in the Day 1 assessment.

Sample problems:

  1. Four charges are arranged in a square with sides of length 3.50 cm. The charges in the top right corneris +2.0 μC and bottom left corner is +4.0 μC. The charges in the other two corners are both –3.0 μC. What is the net force exerted on the charge in the top right corner by the other three charges?
  1. For the charge distribution described in #1, what is the electric field at the center of the square? (magnitude and direction)
  1. A +2 μC charge is located 5.0 cm away from a –2μC charge. Sketch the electric field lines and the equipotential lines around these two charges.
  1. During a 4.00 min interval, a 1.35 A current is set up in a wire. How many a) coulombs and b) electrons pass through any given cross section across the wire’s width?
  1. A small but measurable current of 1.23 x 10-10 A exists in a copper wire whose diameter is 2.50 mm. The number of charge carriers per unit volume is 8.49 x 1028 m-3. Assuming the current is uniform, calculate the electron drift speed.
  1. A copper wire of cross sectional area 2.00 x 10-6 m2 and a length of 4.00 m has a current of 2.00 A. The resistivity of copper is 1.70 × 10-8m. a) What is the resistance of the wire? b) What is the magnitude of the electric field along the wire? c) What is the power dissipated by this wire? d) How much electrical energy is transferred to thermal energy is 30 min?
  2. Three resistors are connected in series to a 15 V battery. If R1 = 25 , R2 = 16 , and R3 = 40 , determine the current and potential for each battery and the current ant total resistance for the battery. Repeat if the resistors are connected in parallel.
  3. Solve the following circuit completely.
  1. Determine the current present in each battery and resistor. Indicate the direction of each current on the diagram.

Image result for Kirchhoff s law practice diagram

  1. A charge of –1.50μC is located on the positive y-axis of a coordinate plane 20.0 cm from the origin while a second charge of +2.50μC is located on the positive x-axis 10.0cm from the origin. Determine the value of the following quantities at the origin.
  2. the magnitude of the electric field,
  3. the direction of the electric field,
  4. the electric potential (assuming the potential is zero at infinite distance), and
  5. the energy needed to bring a +1.0μC charge to the origin from infinitely far away.
  6. Two large, parallel, conducting plates are 12 cm apart and have charges of equal magnitude and opposite sign on their facing surfaces. An electrostatic force of 3.9 x 10-15 N acts on an electron placed anywhere between the two plates. a) Find the electric field between the plates. b) What is the potential difference between the plates? c) If the electron approaches the positive plate perpendicular to the plane of the plate at 3.5 x 105 m/s, determine the speed and direction of the electron when it reaches the midpoint between the plates. d) What is the speed of this electron when it reaches the negative plate? e) If the electron approaches perpendicular to the negative plate at 3.5 x 105 m/s, what is it’s speed when it reaches a point half way through? f) What is the speed of this electron when it reaches the positive plate?
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