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halosh92:
ELECTRICITY:



1)which of the following describes the electric potential difference between two points in a wire that carries a current?
a) the force required to move a unit positive charge between the ponts
b) the ratio of the energy dissipated between the points to  the current
c) the ratio of the power dissipated between the points to the current
d) the ratio of power disipated between the points to the charge moved.

wats the answer and why is it so?

2) two parallel metal plates P and Q are situated 8.0cm apart in air
plate Q is earthed and plate P is maintained at a potential of +160V
a) on a figure draw lines to represent the electric field in the region between the plates


what do they mean by earthed? and wats the direction of the field lines???

astarmathsandphysics:
P=vi so v=p/i answer is b will answer the other when I get home

halosh92:

--- Quote from: halosh92 on March 15, 2010, 07:24:37 am ---ELECTRICITY:



1)which of the following describes the electric potential difference between two points in a wire that carries a current?
a) the force required to move a unit positive charge between the ponts
b) the ratio of the energy dissipated between the points to  the current
c) the ratio of the power dissipated between the points to the current
d) the ratio of power disipated between the points to the charge moved.

wats the answer and why is it so?

2) two parallel metal plates P and Q are situated 8.0cm apart in air
plate Q is earthed and plate P is maintained at a potential of +160V
a) on a figure draw lines to represent the electric field in the region between the plates


what do they mean by earthed? and wats the direction of the field lines???

the magnitude of the  electric field between the plates is 2.0 * 10 ^3 V/m

b) a dust partcle is suspended in the air between the plates. the particle has charges of ( + 1.2 * 10^-15 C)  and (-1.2 * 10^-15 C) near its ends. the charges may be considered to be point charges separated by a distance of 2.5mm.
the particle makes an angle of 35 degrees, with the direction of the electric field.
i) on a figure draw arriws to show the direction of the force on each charge due to the electric field.
ii) calculate the magnitude of the force on each charge due to the electric field
iii)  determine the magnitude of the couple acting on the particle
iv) suggest the subsequent motion of the particle in the electric field



--- End quote ---

halosh92:
3) two horizontal metal plates X and Y are at a distance 0.75cm apart. a positively charged particle of mass (9.6 * 10^-15) kg
is situated in a vacuum between the plates.
the potential difference between the plates is adjusted until the particles remains stationary.
a) state a reason, which plate X or Y , is positively charged
b)the potential difference required for the particle to be stationary between the plates is found to be 630 V. calculate.
i) the electric field strength between the plates
ii) the charge on the particle



4) an electron travelling horizontally in a vacuum enters the region between two horizontal metal plates.
the lower plate is earthed and the upper plate is at a potential of +400V. the separation of the plates is 0.80cm
the electric field between the plates may be assumed to be uniform and outside the plates to be zero
ai) Draw an arrow on the electron to show the direction of the force on the electron due to the electric field between the plates
ii) sketch the path of the electron as it passes between the plates and beyond them.
b) determine the electric field strength E between the plates.
cI) calculate, for the electron between the plates, the magnitude of :
i) the force on the electron
ii) its acceleration
d) state and explain the effect , if any of this electric  field on the horizontal component of the motion of the electron.

vanibharutham:
I have not done fields yet, but i reckon i can try and explain question 1 on electricity

Its useful to learn the definitions:

ELECTROMOTIVE FORCE, is the energy transferred per unit charge from a cell to the circuit... i.e. amount of energy that is converted to electrical energy per unit charge.

POTENTIAL DIFFERENCE, is the energy transferred per unit charge from the circuit to a component and converted to other forms.... i.e. the amount of electrical energy converted to other forms of energy per unit charge

Therefore,

from the definitions above:

Potential Difference = E/Q (e = energy, q = charge)
Learn the things above, they are useful for electricity


P = IV

Therefore,

V = P / I

therefore potential difference is a ratio of power dissipated to the current

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