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kodGreya [7K]
3 years ago
13

A 0.80-μm-diameter oil droplet is observed between two parallel electrodes spaced 11 mm apart. The droplet hangs motionless if t

he upper electrode is 17.8 V more positive than the lower electrode. The density of the oil is 885kg/m3. Part A What is the droplet's mass? Express your answer to two significant figures and include the appropriate units. m m = nothing nothing Request Answer Part B What is the droplet's charge? Express your answer to two significant figures and include the appropriate units. q q = nothing nothing Request Answer Part C Does the droplet have a surplus or a deficit of electrons? How many? Does the droplet have a surplus or a deficit of electrons? How many? deficit 9 electrons surplus 9 electrons surplus 16 electrons deficit 7 electrons
Physics
1 answer:
Arisa [49]3 years ago
3 0

A) 2.4\cdot 10^{-16}kg

The radius of the oil droplet is half of its diameter:

r=\frac{d}{2}=\frac{0.80 \mu m}{2}=0.40 \mu m = 0.4\cdot 10^{-6}m

Assuming the droplet is spherical, its volume is given by

V=\frac{4}{3}\pi r^3 = \frac{4}{3}\pi (0.4\cdot 10^{-6} m)^3=2.68\cdot 10^{-19} m^3

The density of the droplet is

\rho=885 kg/m^3

Therefore, the mass of the droplet is equal to the product between volume and density:

m=\rho V=(885 kg/m^3)(2.68\cdot 10^{-19} m^3)=2.4\cdot 10^{-16}kg

B) 1.5\cdot 10^{-18}C

The potential difference across the electrodes is

V=17.8 V

and the distance between the plates is

d=11 mm=0.011 m

So the electric field between the electrodes is

E=\frac{V}{d}=\frac{17.8 V}{0.011 m}=1618.2 V/m

The droplet hangs motionless between the electrodes if the electric force on it is equal to the weight of the droplet:

qE=mg

So, from this equation, we can find the charge of the droplet:

q=\frac{mg}{E}=\frac{(2.4\cdot 10^{-16}kg)(9.81 m/s^2)}{1618.2 V/m}=1.5\cdot 10^{-18}C

C) Surplus of 9 electrons

The droplet is hanging near the upper electrode, which is positive: since unlike charges attract each other, the droplet must be negatively charged. So the real charge on the droplet is

q=-1.5\cdot 10^{-18}C

we can think this charge has made of N excess electrons, so the net charge is given by

q=Ne

where

e=-1.6\cdot 10^{-19}C is the charge of each electron

Re-arranging the equation for N, we find:

N=\frac{q}{e}=\frac{-1.5\cdot 10^{-18}C}{-1.6\cdot 10^{-19}C}=9.4 \sim 9

so, a surplus of 9 electrons.

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Using I=135 A, the current flowing in each wire, we can calculate the magnetic field generated by each wire at distance 
r=40.0 cm=0.40 m, 
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B= \frac{\mu_0 I}{2 \pi r}= \frac{(4 \pi \cdot 10^{-7} N/A^2)(135 A) }{2 \pi (0.40 m)}=6.75 \cdot 10^{-5} T

Then we can calculate the magnitude of the force exerted on each wire by this magnetic field, which is given by:
F=ILB=(135 A)(222 m)(6.75 \cdot 10^{-5}T)=2.03 N

2) direction of the force: 
The two currents run in opposite direction: this means that the force between them is repulsive. This can be determined by using the right hand rule. Let's apply it to one of the two wires, assuming they are in the horizontal plane, and assuming that the current in the wire on the right is directed northwards:
- the magnetic field produced by the wire on the left at the location of the wire on the right is directed upward (the thumb of the right hand is directed as the current, due south, and the other fingers give the direction of the magnetic field, upward)

Now let's apply the right-hand rule to the wire on the right:
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A similar procedure can be used on the wire on the left, finding that the force exerted on it is directed westwards, so the force between the two wires is repulsive.
6 0
2 years ago
Which of the following is not a reason fluorescent lamps are advantageous over incandescent lamps?A. Fluorescent lamps are more
mr_godi [17]

Answer:

B. Fluorescent lamps operate at a higher temperature than incandescent

Explanation:

Fluorescent lamps have a number of advantages over incandescent lamps which are given in the options given in A, C and D. The option available in B is a drawback, not an advantage. This is because it can give out and radiate more heat as a result of working at a higher temperature. Hence B option is correct.

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3 years ago
What is the net electrical charge on a magnesium ion that is formed when a neutral magnesium atom loses two electrons?
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-3.2x10^-19C is formed 
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A proton moves through a magnetic field at 20.3 % of the speed of light. At a location where the field has a magnitude of 0.0062
galina1969 [7]

Answer:

Force on the proton will be .73\times 10^{-14}N

Explanation:

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Magnetic field B = 0.00629 T

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Angle between velocity and magnetic field \Theta =137^{\circ}

Force on the proton is equal to F=qvBsin\Theta =1.6\times 10^{-19}\times 6.9\times 10^7\times 0.00629\times sin(137^{\circ})=4.73\times 10^{-14}N

4 0
2 years ago
While playing football, Chris runs 4.5 m at 20⁰ south of west. If an opponent was trying to tackle him how far west and south wo
rewona [7]

Answer:

South = 1.5m

West =4.2m

Explanation:

Kindly see attached a rough draft of the situation

Step one

Given data

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Step two:

Hence for an opponent to tackle him towards the south, he must be at

sin θ= opp/hyp

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x=sin 20*4.5

x=0.342*4.5

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Also, for an opponent to tackle him towards the south, he must be at

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y=cos 20*4.5

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5 0
2 years ago
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