AQA Physics P3 May 23rd 2013 NEW SPEC

Original post by sammann123

Which is true but I don't think we have to know that.
What frequency do switch mode transformers work at?

50,000Hz to 200,000Hz if I remember correctly. Let me check.

How does a magnifying glass work?

Reply 382

Fabz_x

1

Good luck for the exam guys :smile:

x

Reply 383

Original post by MsFahima

50Hz

Give an advantage of a CT Scans over X-Rays. (2)

50 kHz actually
Provide a 3D Image
That can be viewed from multiple angles
That allows for greater detail in pre-surgery analysis.

Describe one condition under which electromagnetic induction will not take place.

Reply 384

ChickenTeryaki

Original post by alecbritton

thanks so much!

No problem. Good luck for tomorrow!

Reply 385

Original post by Quantaˌ

50,000Hz to 200,000Hz if I remember correctly. Let me check.

How does a magnifying glass work?

Yeah thats true.
Uses a converging lens? By moving the object away and towards the focal point different magnification is achieved? Not so sure on that one.
How does it work?
And why are step down transformers used in transferring power from overhead cables to the home.

(edited 10 years ago)

Reply 386

Original post by Spag

Think a decent nights sleep will be better than a quiz

I normally work late and I've got to do a lot of revision anyway. I can sacrifice one night for revision...

Original post by sammann123

50 kHz actually
Provide a 3D Image
That can be viewed from multiple angles
That allows for greater detail in pre-surgery analysis.

Describe one condition under which electromagnetic induction will not take place.

When the wire is parallel to the magnetic field lines...

What three ways can you describe an image produced by a lens?

Reply 387

Original post by Quantaˌ

I normally work late and I've got to do a lot of revision anyway. I can sacrifice one night for revision...

When the wire is parallel to the magnetic field lines...

What three ways can you describe an image produced by a lens?

Real or virtual
Magnification
Upright or inverted

What type of lens is used to treat short sight.
Also, what's the opposite of diminished?

Reply 388

Ciaran Cobain

How can I explain how to find the centre of mass in words if this is a 6 marker?

Reply 389

MsFahima

20

Original post by sammann123

50 kHz actually
Provide a 3D Image
That can be viewed from multiple angles
That allows for greater detail in pre-surgery analysis.

Describe one condition under which electromagnetic induction will not take place.

Yeah - I realised I wrote the wrong answer.

When the magnet is not moving, a p.d will not be created so then the electromagnetic induction will not take place.

How can an object be madde more stable?

Reply 390

Helena...

Original post by Quantaˌ

I normally work late and I've got to do a lot of revision anyway. I can sacrifice one night for revision...

When the wire is parallel to the magnetic field lines...

What three ways can you describe an image produced by a lens?

Isn't that for motor effect. I thought it would be if magnet or wire is not moving as there would be no changing magnetic field.

Reply 391

Helena...

Original post by MsFahima

Yeah - I realised I wrote the wrong answer.

When the magnet is not moving, a p.d will not be created so then the electromagnetic induction will not take place.

How can an object be madde more stable?

Larger base, lower centre of mass, base bolted to groground

Explain what a force multiplier is

(edited 10 years ago)

Reply 392

MsFahima

20

Original post by Ciaran Cobain

How can I explain how to find the centre of mass in words if this is a 6 marker?

1) Make holes in the edge of the object. At least 2 holes must be made.
2) Freely suspend the object from the rod, and wait until it stops moving.
3) Using a plumbline, draw a horizontal line from the rod downwards on the object.
4) Repeat for the other holes.
5) Where the lines cross is the centre of mass of the object.
6) To check if this is the correct centre of mass, balance the object on a pencil or other such object on the point where the lines cross.

Something like that.

Reply 393

Original post by Helena...

Isn't that for motor effect. I thought it would be if magnet or wire is not moving as there would be no changing magnetic field.

It works for both, the whole idea is the magnetic field lines cutting each other in both the motor and generator effect. If I'm wrong please explain otherwise :smile:

?

Reply 394

Original post by Helena...

Larger base, lower centre of mass, base bolted to groground

Explain what a force multiplier is

A system where the force is increased or decreased according to the surface area the pressure is acting on. Not so sure about that <<?
Why would it be better to use Ultrasound that X-rays, 3 points.

Reply 395

Original post by Helena...

Isn't that for motor effect. I thought it would be if magnet or wire is not moving as there would be no changing magnetic field.

If the wire doesn't move, it would also not cause induction. But, if the wire is parallel to the magnetic field lines then even if you move the wire you won't cut any field lines...

Original post by sammann123

Real or virtual
Magnification
Upright or inverted

What type of lens is used to treat short sight.
Also, what's the opposite of diminished?

Diverging. And magnified? I'm not sure on the second one.

Original post by MsFahima

Yeah - I realised I wrote the wrong answer.

When the magnet is not moving, a p.d will not be created so then the electromagnetic induction will not take place.

How can an object be made more stable?

Lower centre of mass or widen base. I think that's all?

Original post by sammann123

Why would it be better to use Ultrasound that X-rays, 3 points.

Does not ionise (safer), can detect tissue and can destroy kidney stones.

What is total internal refraction?

(edited 10 years ago)

Reply 396

Original post by Quantaˌ

If the wire doesn't move, it would also not cause induction. But, if the wire is parallel to the magnetic field lines then even if you move the wire you won't cut any field lines...

Diverging. And magnified? I'm not sure on the second one.

Lower centre of mass or widen base. I think that's all?

What is total internal refraction?

Total internal reflection occurs when the angle of refraction is greater than 90 degrees, this occurs when the critical angle of incidence is reached. ahh that sounds like a very dodgy explanation..! I'm not sure how to describe what it actually is?
When the wave cannot pass through and is totally internally reflected. But that's basically just using the words from the question.
How does a CCD device work.

(edited 10 years ago)

Reply 397

Original post by sammann123

Total internal reflection occurs when the angle of refraction is greater than 90 degrees, this occurs when the critical angle of incidence is reached. ahh that sounds like a very dodgy explanation..! I'm not sure how to describe what it actually is?
How does a CCD device work.

I would have said when the angle of incidence is greater than the critical angle.

CCD? Do we need to know this? I would guess at the light hitting the CCD would cause the flow of electricity across the device. This would be detected by a computer and used to create an image. But I have no idea! What would you say?

Reply 398

Original post by Quantaˌ

I would have said when the angle of incidence is greater than the critical angle.

CCD? Do we need to know this? I would guess at the light hitting the CCD would cause the flow of electricity across the device. This would be detected by a computer and used to create an image. But I have no idea! What would you say?

Yeah that sounds about right, i guess its when all of a wavelength is reflected due to the angle of incidence being greater than the critical angle.

CCD's briefly come up. So, when an ionising X ray hits the CCD, an electron is knocked off the surface, this electron creates a charge that can be detected by a computer to form an image.

Give 2 properties of X rays.

Reply 399