electric circuits - Why are we connecting voltmeter in series with power when we measure voltage across it?

I am a physics teacher and demonstrated in the class that the voltage across at wall socket is around 220V ( in Europe ) and my student asked why we are connecting a voltmeter in series with power outlet ( I stated to my students previously that if we want to measure voltage of the resistor, we make a parallel connection with it.) I explained them that we need to think the power source as a battery and the internal resistance of new opened battery is very small compared to the internal resistance of the voltmeter.He came out with the second qu...Read more

Why should a voltmeter have a higher resistance than of any circuit element across which the voltmeter is connected?

According to my textbook, it is said that, for an ammeter: It is essential that the resistance $R_A$ of the ammeter be very much smaller than other resistances in the circuit. Otherwise, the very presence of the meter will change the current to be measured.Which makes definite intuitive sense to me. One would hope its resistance is very low, because otherwise it would be like trying to measure the speed of a car by putting spikes under its tires just before. However, what it says for voltmeters is not intuitive for me: It is essential that...Read more

electric current - Does the resistance of the voltmeter affect the behavior of this circuit?

I have this setup. It consists of a battery of no internal resistance with voltage $V$ and a resistor with resistance $R$. It also consists of a voltmeter of some (not so large) resistance as good ones should have. Now my question is, will the resistance of the voltmeter matter for this particular circuit?I think that the voltmeters need to be high resistance only when there are multiple resistances in the circuit... and as the internal resistance of the battery always contributes to the total resistance in real cases, a voltmeter is always ex...Read more

electric circuits - Loss in energy while charging a capacitor

Suppose a capacitor having capacitance $C$ is being charged using a cell of emf $E$. By the time the capacitor is fully charged, the cell has supplied $QV$ energy while the potential energy of the capacitor is $QV/2$. So there is a net loss of $QV/2$ joules of energy. Where is the energy lost? Since it is an ideal circuit, there is no resistance and there should be no heat loss. Can anyone tell me which assumption do we make and where do we make it while setting up the ideal circuits and deriving their formulas which is the reason for the loss ...Read more

electric circuits - Why would Low Voltage produce HIGH current with the same resistance? Transformers

We always see in Ohm's law that $v=IR $. So if $R$ is fixed for a wire, how can the electrons with High P.D have low current. Isn't it the electrons bumping into the resistor that creates the heat? Doesn't the rate of electrons bumping into the atoms of the resistor determine how much energy is dissipated from the resistor? If so how can charges store the P.D (High Voltage) in them when they move through the powerlines with a low current....Read more

electric circuits - Output in a half wave rectifier

In a half wave rectifier only a single diode is present. One end of the secondary wire of the transformer is connected to the p side of diode while the other to the load resistor. The n side is connected to the load resistor. When the diode is reverse biased no current passes through it. But current does pass through the other wire of the secondary which eventually meets the load resistor . So wouldn't the output in this case be an ac current?...Read more

electric circuits - Saturated BJT Transistors. V CE < V BE : AKA - Things that make you go “Hmmmm”

At the risk of being blasted for cross-posting, I am posting this question again here in the Physics department. It is a duplicate of this post in the EE forum. However, I would like to get some answers from more of a Physicist perspective and less of an Engineer. I don't like the fact I have to post it twice either, but I don't know how else to get the right audience to answer it here on StackExchange.We use them every day and those in the know fully understand the functional characteristics of BJT transistors. There are documents and links ga...Read more

electrical resistance - Circuit Analysis - Grounding and Current

Just starting to learn basic concepts of electronics, and I'm a bit confused looking at this diagram. Previously, we've always had a wire connected to the negative end of the terminal, and that made sense as electrons flowing from negative to positive would re-enter the battery. In this case, how can current flow? Maybe I'm misunderstanding, but this doesn't seem like a closed circuit? I feel like I'm also pretty shaky on ground, but if the only path for electrons is to ground, how can there be a voltage difference? Also, where does current flo...Read more

electric circuits - Help with $I$-$V$ Characteristic of a Diode

I am struggling to understand why I can't get a full voltage range when I have the diode the correct way round. If you check this link:https://electronics.stackexchange.com/q/266201/If you look at the answer I have set my circuit up like circuit 2. I have a rheostat and have put the diode in parallel and I am using a 3V battery. When the diode is the wrong way round I get a range of 0-3V when I slide the rheostat. When it is the correct way round I only get 0-1V. When it is at 1V, the p.d. across the battery is still 3V. Where is this missing 2...Read more

electric circuits - Question about full wave bridge rectifier

Sorry if this is a stupid question, what I know is when a diode is forward biased, it conducts current, when it is reverse biased, it acts as an open branch if its $ PIV \geq V_{in}$ But in this picture:At the node between $D1$ and $D3$ ,$D1$ is forward biased and $D3$ is reverse biased, so that's fine, now at the node between $D2$ and $D3$ why does the current pass through $D2$ and not $D3$? Isn't $D3$ supposed to be forward biased at that junction too? Thanks....Read more