Unit 4 Flashcards
(32 cards)
What is gravitational field strength?
The force per unit mass at that point.
What is Newton’s Law of Gravitation
Two particles attract each other with a force that is proportional to the product of their masses and inversely proportional to the square of their separation.
What is gravitational potential?
The work done in moving a unit mass to that point from infinity, where the potential is defined as zero
What is the relationship between gravitational field strength and gravitational potential?
The gravitational field strength is equal to the magnitude of the gradient of the graph of gravitational potential against radius, at any given radii.
What are the characteristics of a geostationary orbit?
Period = 1 day Orbiting above the equator. Same direction as the earth
What are the conditions for escape? (Reaching the escape velocity)
The kinetic energy must raise the gravitational potential to zero.
What path does a particle in a uniform gravitational field take?
Parabolic
What is Coulomb’s Law
The force between two charges is directly proportional to the product of their charges and inversely proportional to the square of their separation.
What is Electric Field Strength?
The force per unit positive charge at that point.
What path does a charged particle in a uniform electric field take?
Parabolic
What is ‘electric potential’?
The work done in moving a unit positive charge to that point from infinity, where the potential is defined as zero.
What is the relationship between ‘electric field strength’ and ‘electric potential’?
The ‘electric field strength’ is the gradient of the graph of ‘electric potential’ against ‘radius’.
What is capacitance?
The capacitance of a capacitor is a measure of its ability to store charge. See formula.
What happens to the charge, current and potential difference across a capacitor as it discharges.
They undergo exponential decay. See formula.
How do p.d. and charge vary with time whilst charging a capacitor?
The increase following a ln curve starting at the origin.
How does current vary when a capacitor is charging with time?
It decreases following an exponential decay.
Explain the distribution of p.d. during charging if a capacitor through a resistor.
At first no charge on capacitor so no p.d. All the supply p.d. across the resistor. As charge builds up on the capacitor the p.d. across it rises and the p.d. across the resistor falls. When fully charged the p.d. across the capacitor reaches that of the supply voltage and the p.d. across the resistor is zero.
What is ‘magnetic field strength’/’magnetic flux density’?
The magnetic force per unit length per unit current on a current carrying conductor at right angles to the field lines. Measured in Teslas.
What is a ‘line of force’ of a magnetic field?
A line at which a ‘free’ North Pole would move in the field.
What is Faraday’s Law?
As a magnet moves through a coil the induced emf increases if: •The magnet is moved faster. •The magnet is stronger •There are more turns on the coil •The cross sectional area if the coil is increased
What path do charged particles in a magnetic field follow and why?
The path is circular because the force is always at right angles to the motion.
What is ‘magnetic flux’?
The magnetic flux is a measure of the number of magnetic field lines passing through a region.
What is ‘Lenz’s Law’?
The induced emf will be such that it would produce a current in the coil which will oppose the change producing it.
How do you calculate induced emf?
The product of the magnetic field strength and the area swept out per second.
