ELECTROSTATICS
Electric Fields
Simple circuits
100
What is the elementary unit of charge?
The smallest unit of charge (1.6x10-19C)<-On the reference table
100
What is the formula for mechanical and electrical power. HINT: On reference table
Mechanical: P=W/t=Fd/t=Fv Electrical P=IV
100
What is the difference between direct current(DC) and alternating current (AC)?
Direct current travels in one direction and alternating current flows in two directions or oscillates.
200
What is Coulomb's law?
Fe=Kq1q2/r^2
200
How much power is dissipated by a mini light bulb connected to a 1.5V battery drawing a current of 28mA?
P=IV=(1.5V)(.028A)=.042W
200
What is electric current and what is the formula to find it? HINT: you can look on the reference table
It is the rate in which charge flows. I=deltaq/t
300
When a neutral metal sphere is charged by contact with a positively charged glass rod, the sphere 1. loses electrons 2. gains electrons 3. loses protons 4. gains protons
1. loses electrons Explanation: to make something + we have to make it less - and to do this we woud need to lose electrons because protons (for the most part) can not be removed from an atom.
300
How do you work out electric field strength and answer this question: A charge of +1x10^-5C experiences a force of .2N when placed at a point in the electric field produced by a negativly charged sphere. What is the magnitude and direction of the electric field strength at that point?
E=Fe/q E=.2N/(1x10^-5C)=20000N/C inward
300
If a 12A current is allowed to flow for 20s in a circuit a) how many coulombs of charge pass a single point in that circuit? b) how many charge carriers pass that point?
a) q=It=(12A)(20S)=240C b)240C/1.6x10^-19C=1.5x10^21e
400
The electron and proton in a hydrogen atom are separated by approximately 10x10-10m. Find the magnitude of the electric force.
Fe=kq1q2/r^2 Fe-9x10^9(1.6x10^-19c)(-1.6x10^-19c)/((1x10^-10m)^2)= 2.3x10^-8N
400
What is the formula for resistance and answer this question: A wire has a resistance of .1 ohms and is connected directly to both ends of a 1.5 V battery. What is the current in the wire?
Formula: R=V/I I=V/Ohms I=(1.5V)/(.1ohms)=15A
500
What are the 5 properties of electric field lines?
1. the never cross 2. they show the direction of force on a small positive test charge 3. go from positive into negative 4. the direction of electric force is tangent to the curved field lines 5. density and field lines are proportional to field strength
500
Using table of resistivities and equation R=pL/A answer this question: What is the resistance of a nichrome wire 12 m long with a distance of 2.7x10^-4m?
R=(12M)(150X10^-8ohms*m)/(2.7x10^-4m)=.067ohms
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