Electric and magnetic field questions

Question 1

Electron means amber in what language? ..........................................

a Interpret the symbols in the equation giving the units.

f = 1/4peo (q₁q₂/d²)

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b Define voltage

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c In what simple way can a uniform electric field be established?

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d Why is Coulomb remembered as the force law person?

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e Write down the two definitions of electric field strength as equations where the symbols have their usual meanings.

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f The electron Volt is a unit of ............................

g Why do electric field lines never cross?

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h How does the potential near a point charge depend on distance from the charge?

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i How do electric field lines intersect the surface of a charged conductor?

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j Taking account of your answer to the last question - why is the surface of a charged conductor always an equipotential?

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k Convert 2.0 eV to Joules ..................................

 

Question 2

a The unit of electric charge is the ..........................................

b Interpret the symbols in the equation giving the units.

V = IR

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b What is the most important fact about current in a simple series circuit of one loop?

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c What is the most important fact about voltage in a simple series circuit of one loop?

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d What is the voltage across a resistor of 5 ohms carrying 10 Amps?

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e Two resistors of 2 Ohms each are placed in series - what is the total resistance?

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f Two resistors of 3 Ohms each are placed in parallel - what is the total resistance.

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g What is the symbol for ohms?

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h What is the origin of the battery (DC power supply symbol?

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i What does DC mean?

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j Write down the three forms of the electric power formula.

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Question 3

What is the symbol for magnetic field strength?

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a Interpret the symbols in the equation giving the units.

f = BIL

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b Draw an arrow to show the magnetic field around this wire?

c A conventional current is a flow of ........................... charge

d Why has the original definition of the direction of current flow never been changed?

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e In which direction is the uniform magnetic field shown below?

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f In which direction is the force on a current flowing upwards in the plane of the page (screen) in the magnetic field?

X X X X X X

X X X X X X.

X X X X X X

X X X X X X

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g What will be the path of an electron injected into this magnetic field from the left in the palne of the page (screen)?

X X X X X X

X X X X X X.

X X X X X X

X X X X X X

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h The formula F = BIL applies to electric current that is perpendicular to a magnetic field.

What is the corresponding formula when a charged particle q moves with velocity v perpendicular to a magnetic field?

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i What is the force on a current parallel to a magnetic field?

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j What is the shape of the path of charged particle moving in a magnetic field with a velocity that is in some direction not perpendicular to the field?

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Question 4

a The unit of magnetic flux is the Weber.

Define flux. ..................................................................................

b Interpret the symbols in the equation, giving the units where appropriate.

V = - d/dt F

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c What is the name given to the equation in part b above?

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d When a plane over the North Pole through the vertical magnetic field of the earth a small voltage appears across the wing tips. What equation is required to calculate the size of the voltage.

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e Dr Jacobs likes to describe the equation that is the answer to part d above as the "lawn mower equation".

Explain why. .....................................................................................

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f A loop of wire is placed at right angles to a strong magnetic field.

Why, in terms of flux, is there no voltage induced in the loop when it is stationary.

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g Write down two ways in which a voltage can be induced in the loop of part f above.
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h What is a Hall probe used to measure?

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i Why is a hall probe made with silicon and not copper, which is a better conductor?

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