Electromagnetism Questions

hello and welcome to this video where we're going to look at some questions and answers on magnetism and electromagnetism topic so let's get started so in this first question student has set up an experiment to investigate the magnetic field around the current carrying wire we need to describe how the student could use this experiment and compass to investigate the magnetic field produced by the wire so what do we need to do well number one they're going to place the compass onto the card so they're going to be placing it here they're then going to observe the direction the compass points and when they've done that they're going to plot and draw that line once they've done that they'll then move it around into different locations and can also consider different distances okay question 1b draw the shape of the field which will be found around this wire well we know that in this example the field is going to be circular field around the wire like so with the wire running through the middle now as well as this we need to give the direction for this we're going to use the right hand rule so we get our right hand and we make thumbs up symbol like this we then need to consider which way the current is traveling so here you can see in the diagram that is showing that it's going at the top and down the bottom so we need to rotate our thumb and so that it travels in the direction of the current which is down and then when we look at which way our fingers are pointing you can see they're moving around here in clockwise direction so our arrow lines going to show that the magnetic field lines are moving in clockwise direction part the behavior of magnetic compass is evidence that the core of the earth is magnetic explain why while compass will always point to magnetic north and this is because it's lining up with the earth's magnetic field okay on to the next page in this question two students and are using different methods to see magnetic field patterns student is using compass to plot magnetic field pattern we need to describe how they could do this and we can draw diagram so what the first thing we're going to do is we're going to place the magnet on sheet of paper so we've got our sheet of paper with our magnet on then we're going to place the compass near the end of the magnet like so and we're going to mark position where the needle points we're then going to repeat this for different locations around the compass in this question here we need to sketch the fill pattern that the student would find around the bar magnet our sketch should show the direction of the field pattern so we're drawing our lines we're going to draw couple of lines on each side like so we can even have some lines coming in and out we also therefore need to draw the arrows the arrows for direction of field plan always travel from the north to the south so it's going away from the north towards the south so they're going to look like this in it tells us that two students are investigating the magnetic effect of current carrying wire look at the graph of their results what is the trend shown by the graph well for the first mark we always want to use the axes title so as the distance from the wire increases the magnetic field strength decreases and we can see this because it's got negative correlation how we're going to pick up our second mark we're looking at this we can see that it decreases in non-linear pattern what mean by that is it's not straight line for decline it's this curve where it decreases rapidly at the start and then starts to slow down as it levels off okay on to the next page in this question our figure shows the magnetic field produced by current in long straight wire which row of the table is correct when the strength of the magnetic field is greatest well let's have look so when it's at its greatest magnetic field the distance is going to be small and the current is going to be large so it can't be this one it's going to be that one we can check our other ones so we therefore know the correct row is which of these materials would be the most suitable for making temporary magnet temporary magnet needs to be magnetic material and the only magnetic material that we've got there that would lose its magnetism easily would be iron steel which is made majority of iron will hold its magnetism quite long time so it wouldn't be very good temporary magnet and finally last one this magnet this figure shows magnet holding some paper clips describe how students show that the paper clips are induced magnets well induced magnets only have magnetism when they're within another magnetic field so the way that we would do this is we would remove the magnet from the paper clips and they would no longer attract each other as this paperclip here for example is only attracting this one because it's becoming temporary magnet an induced magnet because within the magnetic field of this magnet this permanent magnet so if we took the permanent magnet away this magnet would no longer be within that magnetic field we would no longer be acting as an induced magnet and therefore would not attract the second or the third paper clip okay let's move on to our next question okay so in this question we're looking at solenoid which is this coil of wire here and we've got some information about the solenoid we need to draw lines on the figure below to show the shape of the magnetic field just within the solenoid so within the solenoid our films our magnetic field is strong and uniform so we're going to draw nice parallel lines roughly evenly spaced out going through the middle of our solenoid we have to worry about what happens outside because it's only asking us the magnetic field inside the solenoid how could student determine the shape of the magnetic field around the solenoid they could do this in exactly the same way that we've done previously so they replace the compass on card and draw the direction the compass is pointing and then again you would repeat that for different locations nice quick page let's swiftly move on so here the student is investigating the magnetic properties of three rods so each rod is made of one of the following materials so we've got soft iron steel and wood they place each rod within the solenoid and they connect it to the power supply and they test the magnetic strength by seeing how many paper clips it can pick up which we've got here you see before when there's current and then one minute and 10 minutes after the current switched off we need to complete the table to show which material each rod is made from and give the reason why that part of the table has been done for us so let's use information from the table above so rod we can see that does is not magnetic so when we look in r3 we've got soft iron steel and wood it's quite clear that would be made from wood the other two are magnetic now we've got decision to make about the others so when we look at and so we're looking here in our table we can see that both of them do pick up paperclips when they're within when there's current within the solenoid so it could be either of those two now the key thing is what happens afterwards you can see that one minute afterwards this one only has one was this one has seven and after ten minutes has lost everything every paper clip where still has seven so is holding on to the electromagnetism longer than so soft iron can very quickly lose its magnetism so that'll be whereas steel which holds the magnets for lot longer after the current is turned off must be so we can work for reason the soft line only attracts paper clips when there is current whereas the steel attracts when there is current but also after in our next example we've got magnet producing magnetic field which diagram shows the magnetic field pattern around the bar magnet tick one box well we know that the magnetic fields are strongest near the poles so it's going to be nice and close together the field lines near pot so we know it's definitely not going to be one of these two and then we need to decide between these now the only difference between these you can see is the arrows and so anything about which way the arrows go remember the arrows always go from north to south so if we look at these arrows here we can see that they're the wrong way around meaning the only one that's left that's correct is this one from the north to the south that's where those arrows are going this diagram shows three metal blocks so we've got our three metal blocks here they're not labeled one of them is permanent magnet one of them is iron and one of them is aluminium so how could we use another permanent magnet to identify each of these blocks we'll start off with the aluminium so aluminium isn't one of our three magnetic elements iron cobalt and nickel so therefore we know that the permanent magnet would not be attracted to it so aluminium is not attracted to the permanent magnet next we can do the iron so the iron one will be attracted to the permanent magnet and then we can do the permanent magnet which will be attracted just like the iron but to be able to tell the difference it will also have an opposite pole and so it'll be repelled by the permanent magnet so let's make it really clear for our iron it will only be attracted to the permanent magnet so the aluminium won't be attracted the iron will only have force of attraction and the permanent magnet will have both force of attraction and force of repulsion so our final question is the six marker here the diagram below shows toy crane the toy crane uses an electromagnet to pick up and move the blocks explain how this electromagnet is able to pick up and move the blocks so electromagnets obviously can be turned on and off with electricity and that's the key thing here so we could talk about points so for example if we turn the circuit on this will turn the electromagnet on there'll be current in the coil of wire so this will produce magnetic field the iron core will therefore become magnetized and so the blocks will be attracted to the magnet and then by moving the crane the blocks will also move and then finally just to finish up to chop the blocks turn the circuit off and that's been plenty of marks to get us our six marks so hopefully you're answering those questions and you can see anything that you've missed out check out our other videos on electromagnetism and other questions make sure you subscribe and as always happy sciencing