It depends on the nature of the supergiant and the white dwarf. A new white dwarf might have a temperature of 100,000 kelvin so much hotter than any supergiant, but important to in that it is constantly cooling because the star is dead and there is no fusion.

A blue supergiant is a new star with a fusion temperature of around 20,000 kelvin. A red supergiant might be cooler than this, maybe 4,000 kelvin. As long as stable fusion is happening these temperatures remain pretty constant.

If you remember that a white dwarf is a dead star then comparing surface temperatures will depend on how long it has been cooling. Eventually it will be the same temperature as the universe itself so really cold. So it will either be hotter, cooler or the same temperature! 😆

Physics

Would the surface temperature. of stars classified as white dwarfs be generally higher or lower than that of stars classified as supergiants?

It depends. 

The ‘sidereal day’ is 23 hrs 56 mins (and a few seconds) - and that is the time for the stars to appear to revolve around us (remember that the stars don’t actually move around us like they appear to!!) ...so imagine looking up at a star in the sky and spending a day watching it and timing it travel a circle and go back to where it started from. That would take 23hrs 56minutes.

But 24 full hours is the time we measure as one day on our clocks.

How long does it take for the earth to rotate on its axis?

Energy transfers from a place of high energy to one of lower energy. Every single time!

How do you describe the transfer of energy?

Have you had any lessons at all in school that you can work from? 

Learning is about taking time, (lots of time) and revisiting what you have been taught. Identify what you understand and what you don’t understand. Practice what you do understand until you can do it without looking up the answer. Then ask for help with what you don’t understand.

I want to learn physics. Where should I start?

The official answer is ‘the sum of forces acting on an object’ but what does that mean?

A pair of opposite forces will have an effect on the movement of an object. (Like tug of war!) It will move in the direction of the bigger force. So if it’s not moving it will start to move if it is already moving it will speed up or change direction. 

When take the small force from the big force, you get the overall force the object experiences, and this is what we call the resultant force. For example 6N - 3N = 3N. The resultant is what you have after you do this. The bigger the resultant force the bigger the effect. 6N - 1N = 5N so this would be a bigger acceleration.

If the forces are the same as each other, the object won’t accelerate or change direction. Doing the maths again the overall force is zero. So there will be no effect - the object will continue to move without speeding up or slowing down - or not move at all.

What is a summery of a resultant force acting on an object

One thing is does is provide the centripetal force for circular motion around the sun. Which means gravity is the reason the planets don’t all drift through the universe in straight lines.

How does gravity affect the solar system?

In parallel, the total resistance is found by using 1/total resistance = 1/R1 + 1/R2... so in this case 1/total resistance = 1/10 + 1/8 + 1/4.

As this is a parallel circuit you always have the same p.d across each resistor.

Then, the current is calculated using Current = p.d/resistance of each resistor. (Remember the p.d is the same as the source).


How to do calculate the A) total resistance B) the current in each resistor C) the P.D across each resistor. The battery is 20V then going from the positive terminal there is a parallel circuit with 10ohms and 8ohms which then connects to a 4ohms res

A dive into the complete topic of atomic theory and radiation. These lessons cover ions, isotopes, radioactive decay and emissions - including the properties of each of these, half-life and contamination and irradiation. It is big and packed with info!

GCSE

Atomic Theory and Radioactivity

A basic overview of the GCSE electricity topic including static electricity, voltage and current, resistance and some past paper questions.

What is Electricity? A GCSE refresher course

Three videos covering nuclear fission and how we use it to make electricity and the life cycle of stars through an understanding of fusion.

Fission and Fusion

A series of 5 videos that explain the momentum topic at GCSE level with worked examples and exam questions.

What is Momentum?

Following on from the basics of current and potential difference, this series shows how they behave in the two types of circuit. Also included is a discussion of resistance and it's effects.

Electricity 102 : Series and Parallel Circuits

For any student who feels that they missed the core idea about energy. These lessons include: Types of energy, measuring energy, energy stores, energy transfers and energy efficiency. Power is also covered at a basic level. Example exam questions are included.

Jennifer Taylor

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University of Liverpool

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Jennifer Taylor