Topic 2 Energy Flashcards
What is the SI unit of energy?
Joules (J) are the SI units of energy.
What are the units of power?
Power is measured in watts (W). One watt is equivalent to one joule of energy being used per second.
What is a kilowatt hour (kWh)?
This is the amount of energy that something with a power of 1 kW would use if it ran continuously for 1 hour.
What is electric current?
The flow of charged particles. Current (I) is the rate of flow of electric charge (Q), so
I = Q / t
The unit of current is an ampere (A).
What is the conservation of energy?
Energy cannot be created on destroyed, so must always be accounted for.
How are speed and mass proportional to kinetic energy?
Mass is directly proportional to kinetic energy.
Kinetic energy is directly proportional to speed squared.
Expressed by the equation. Ek = Cv^2
Where C is a constant value that relates kinetic energy to the speed squared.
How to calculate the proportionality of forces?
You can divide one by the other i.e.
Ek at 100mph / Ek at 71mph = C x 100^2 / C x 71^2
=(100/71)^2
=1.4085^2
=1.98 =2
The ball traveling at 100 mph has twice the kinetic energy of the ball traveling at 71 mph,
Kinetic energy equation
Ek (J) = 1/2 mv^2
Where m is in kg and v is m/s.
Equation for gravitational potential energy
Eg (J) = mgh
Where m is mass (kg), g is acceleration due to gravity (9.81 m/s/s on earth) and h is vertical height (m) of the object.
Equation for speed of falling (no air resistance)
V = gt
Where g is acceleration due to gravity (9.81 m/s/s) and t is time (s)
Equation for speed of falling (no air resistance)
V = gt
Where g is acceleration due to gravity (9.81 m/s/s) and t is time (s)
Calculate final speed
v^2 - u^2 = 2gΔh
Where v is final speed, u is initial speed, g is acceleration due to gravity and Δh is change in height.
Calculate final speed
v^2 - u^2 = 2gΔh
Where v is final speed, u is initial speed, g is acceleration due to gravity and Δh is change in height.
Planets gravitational potential energy equation.
Eg planet = - (G Ms(sun) m(planet)) / r
Where g is newtons gravitational constant (6.67x10^-11), M is the mass of the sun (1.99x10^30 kg), m is the mass of the planet and r is the radius
What is electrostatic potential energy? (Equation)
The potential energy that an object has because it is electrically charged.
The change in electrical energy (ΔEelec) when electric charges (Q) moves through a voltage difference (ΔV) is given by the equation
ΔEelec = QΔV
What is potential difference?
This is related to the potential energy of a charged particle. it is the measurement of the difference between a reference point and the potential energy available.
Measured in volts.
Electric Potential energy equation.
Eel = VQ
Where Eel is in J, V is volts and Q is is charge in coulombs (C)
Measure potential difference and equation
To measure potential difference you place your reference probe anywhere and your test probe anywhere else. You can then subtract your reference point from your test point.
Potential difference = test probe potential - reference probe potential
Converting mAh to coulombs
1 amp = 1 couloumb per second
So 860 mAh = 0.860 C/s x 3600 s =4644 J = 4.6 kJ
What is work? (Equation)
This is the amount of energy transferred when by applying force to an object.
Work (J) = force applied (N) x distance moved in the direction of force (m)
W = F x I
What is pressure? (equation)
Pressure is defined as the force acting on an object per unit area.
Pressure (P) (Pa) = Force (F) (N) / area (A) (m^2)
Equation for work done on gas.
Work = pressure x change in volume
W = PΔV
Key point: the potential energy of matter.
The arrangement of particles in matter has a potential energy associated with it.
What is heat?
Heat is the transfer of energy that occurs due to a temperature difference.
