Fields and their consequences Flashcards
On a diagram what does the distance of the field lines represent?
Represents the strength of the force by the field
How are Gravitational and Electric fields formed
Gravitational fields - interaction of masses
Electric fields - interaction of charges
Similarities of electric and gravity fields
- both follow inverse square law
- both use field lines to be represented
- both have equipotential surfaces
Gravity is always what?
Always attractive and acts on any object with a mass
What does Newton’s law of gravitation show?
Shows that the magnitude of the gravitational force between two masses is directly proportional to the product of the masses.
Moreover the gravitational force is inversely proportional to the square distance between the centre of masses
What are the two types of gravitational fields
Radial fields and uniform fields.
What is the difference between radial fields and uniform fields?
Uniform fields the strength of gravitational force is the same throughout whilst in radial fields the force depends on the position of the object.
How does gravitational field strength vary in different fields
Uniform fields - remains constant (g = f/m)
Radial fields - may vary (g = GM/r^2)
What is Gravitational Potential
(V) is the work done per unit mass when moving an object from infinity to a point
Gravitational potential at infinity is zero, that is why gravitational potential (V) is always negative
Radial fields: V = -GM/r
What is gravitational potential difference
The amount of energy needed to move a mass from two points
Work done = m * change in V
What is known about equipotential surfaces? refer to work done
No work is done when moving along an equipotential surface as potential (V) is constant
How can you workout gravitational field strength on a diagram
Find the gradient in a V-r graph
When you plot (g) against (r) how do work out the gravitational potential difference
It is the area under the curve
What is Keplers 3rd law
Square of an orbital period is directly proportional to the cube of the radius
T^2 = r^3
How can you derive keplers third law
Centripetal force = gravitational force
Plug in V=2pi(r)/T
How do you work out the total energy of a satellite
Kinetic energy + potential energy (this is constant)
e.g if height of satellite decreases, the potential energy decreases, however the kinetic energy increases at it will travel at a higher speed therefore total energy is kept constant
What is escape velocity?
Escape velocity of an object is the minimum velocity it must travel at in order to escape the gravitational field at the surface of a mass
Kinetic energy = potential energy
1/2mv^2 = GMm/r
What is a synchronous orbit
It is when the orbit of the satellite aligns with the orbit of the mass it is orbiting
What are geostationary satellites
They orbit directly above the equator
Stay at the same point above earth
Used for TV and telephone signals
What are low orbit satellites
Fast moving satellites with smaller orbital periods
- used to monitor the weather and military applications
What is electric field strength
The force per unit charge experienced by an object in an electric field
E= F/Q
E = V/d (uniform field formed by parallel plates) (V is potential difference between plates)
E = Q/4(pi)(epsilon)(r^2) for radial fields
What do electric field lines show
Shows the direction of a positive charge
On an electric field graph against distance what does the area indicate
The electric potential of the sphere
How does the radius of an ion differ when entering the same magnetic field at the same speed due to mass
As centripetal force acting on the ion is influence by mass, if they’re isotopes then their masses would differ hence their radius path would differ.
State Newtons law of gravitation
The attractive force between two point masses
proportional to the product of the masses
inversely proportional to the square of the distance apart
Explain why pendulum closer to a mountain would not point towards the centre of the earth
They’re gravitationally attracted to the centre of gravity of the mountain
`describe two essential featured of the orbit needed for the satellite to appear geostationary
- equatorial orbit
- time period of 24 hours
- moves from west to east
How does a satellite moving to a higher orbit affect the signal strength and contact time of the signal?
- signal would be weaker as the distance it travels is greater
- intensity decreases as distance increases
- signal is received for longer due to a wider beam width due to low angular speed
Define escape velocity
Minimum speed needed for an object to escape a gravitational field
