34
I am used to smoothing out badly shaped circuits by pulling the wires:
Then I get a better circuit by cutting the extra wires:
So there are three resistors in parallel, indicating that the current flows through three possible paths.
29
Your home circuit does not "know" how much current to deliver to each socket or appliance. The circuit supplies a constant voltage, and it is then up to each appliance to limit the current that it draws. Some simple appliances, such as lights with old incandescent bulbs or electric toasters or irons, are basically just a resistor (possible a ...
21
It will normally just reach the negative terminal. Generally, current only flows in closed circuits. Hence, it could only flow into the ground if the positive terminal was also connected to ground, for example if you touch the positive terminal and you stand on the ground with bare feet or so.
Then you might ask, what the purpose of grounding is. The ...
20
There is already a good answer here, but I would like to add that a so-called "15A socket" is not so called because it "contains" 15A. The power grid and the wiring in your walls are capable of delivering hundreds or thousands of Amperes to any socket in your home. At least, it could do so for a brief interval before the smaller wires ...
10
Electric supplies to homes and industries are standardized in countries. This allows devices which are used in homes or in factories to be accordingly designed. For e.g. if the standard single phase RMS AC supply voltage is $240$ V, appliances would be designed such that they operate without electrical failure at that input voltage. What I mean by this is ...
8
Since this is a physics q and a, a physics explanation is in order.
There are two kinds of current.
Conduction current is a net flow of charges. It is was people usually think of when the word "current" is used
Displacement current is another form of current, first recognized by Maxwell. Displacement current plays an essential role in Maxwell's ...
5
Current follows the least resistance path when available.
This is wrong. Recall the Ohm's Law
$$V=IR\Rightarrow I\propto \frac{1}{R}\ \ \ \ \ \ \text{if V constant.}$$
If there are two resistance one having resistance $1\ \Omega $ and the other $2\ \Omega$, connected in parallel then this doesn't mean that if the current will flow through $1\ \Omega$ ...
5
(continued from the previous answer by SG8)
Another way to think about this problem.
First:
Second:
Finally:
5
Voltage, current, and resistance are in a relationship: $V=IR$. This isn't to say that one "causes" the other. We don't always say that voltage "causes" resistance. It's just a relationship that's due to the laws of physics. If you change one variable in that equation, one or another must change.
Now, in the cases you are interested ...
4
If you re-arrange the diagram you will find the you have three resistors in parallel. Another way to see this is to realise that (if we assume $V_A>V_B$) current flows from left to right through the first and third resistors, but from right to left through the middle resistor - so there are actually three paths from A to B, each with resistance $R$.
4
how is it possible that current flows in a circuit with capacitor
since according to Ohm's law current is inversely proportional to
resistance and insulator by definition has a big resistance, so we
basically have an open circuit?
The short answer is because electrons can flow to and from a capacitor without the electrons having to pass through the ...
4
To very briefly summarize the other answers:
A power source is characterized by its voltage only.
A power consumer is characterized by its resistance only.
The combination of the two determines what the current will be (Ohm’s law: $I=\frac{U}{R}$).
If the resulting current is too much, bad things will happen. At best, an overcurrent protection device will ...
3
As shown in other posts the calculated drift speed of electrons in a metal is "surprising" low, $\approx 10 \,\rm \mu m \,s^{-1}$.
A simple demonstration can be set up to illustrate this low speed for coloured ions rather than electrons which are difficult to observe directly.
A filter paper is placed on a microscope slide and saturated with ...
3
Why is voltage same for the two resistors connected parallel in circuit?
If there are no time-varying magnetic fields involved, voltage difference between two points is path independent. It is like altitude on a mountain. Suppose you are on top of a mountain, and there are different paths from the top to your car in a parking lot. The distance you travel ...
3
$11 W$ means the bulb uses 11 watts of power when it's operating at the rated voltage. If you run it for an hour for example, it will cost $0.011 kWh$, and your power company will bill you for ___ (check your local electricity prices).
You can also calculate how much current the bulb will draw since you know the voltage, as well as the resistance of the bulb ...
3
... resistance is caused due to collision of electrons with dust and impurities inside a metal ...
I am not sure where you get "dust" from (I don't think this is mentioned in the video ?), but the flow of electrons through a metal such as copper is certainly impeded by imperfections in the metallic lattice, by the presence of impurities (atoms of ...
3
The removal of electrons from the capacitor plate connected to the + terminal constitutes a current. As those electrons are removed for that plate, there is an accumulation of electrons on the other plate. That movement of electrons constitutes a current.
The current stops when the potentials of the capacitor plates are equal to the potentials of the ...
3
The presence of a parallel-plate capacitor means that in part of the
circuit (only a small part; capacitors rarely have a gap as large
as one millimeter) there is no movement of electrons, only a buildup
of field (accompanied by electrons if the capacitor is not a vacuum
type). This is problematic, because there is a simple way of detecting
current, ...
3
How does the electric circuit in our home „know” how much power to deliver to each socket?
It doesn't. It will supply as much as the appliance demands, up to a point.
How does a home appliance limit the amount of current that flows through it?
It depends on the appliance.
The simplest type is pure resistive, like a kettle or toaster. The resistance of the ...
2
This is a great opportunity to teach your students about performing an energy balance, about various heat transfer modes, about solving differential equations (or approximating them with finite-difference equations), and about model simplification.
For any small section of the wire (length $dx$, cross-sectional area $A$), we can perform an energy balance ...
2
Yes, electrons are at all times in random motion proved from the fact that the material has a macroscopic temperature. The kinetic motion we define as thermal energy and measure as a temperature comes from the random motions, fluctuations, vribrations etc. of the constituent particles of the material incl. the electrons.
With random motion of electrons in ...
2
Voltage in a circuit is defined in terms of energy per charge (J/C). So for simplicity, imagine the simplest parallel circuit with one battery and two branches with a resistor each. Now imagine electrons flowing around this circuit. The battery gives each electron the same amount of energy. So when the electrons leave the battery and reach the first fork in ...
2
You can see this by realizing the upper and lower path are completely symmetric. Thus the current through each of them must be the same. And if the same current is flowing through resistors with the same resistance (the two diagonal ones on the left), the voltage drop across them is exactly the same. Therefore, the topmost and bottom-most corner are at the ...
2
Disclaimer: electricity is extremely dangerous. Please don't play around with your home's main electricity. You could badly injure or even kill yourself. This is especially the case if you live in a country that uses $220~\rm V$ or higher.
There are a lot of things that can factor into you receiving an electric shock or not. But the general idea is that you ...
2
The answer is yes and no.
If a wire has zero voltage across it, and also zero resistance, then by the voltage-current relation
$$V = IR$$
it is consistent that $I = 0$, but it is also equally consistent that $I$ has any nonzero value. Basically, a zero-voltage zero-resistance wire can carry any current one likes. And this part isn't just fantasy: we do have ...
2
Zero resistance only implies zero potential difference in steady state.
If you apply a potential difference across a zero resistance component (such as attaching a wire directly to the battery poles) then charge will start flowing and accelerate and accelerate and accelerate... The electric force due to the potential difference is unrestricted due to no ...
2
Yes, the current would flow, its value being determined by the internal resistance of the battery.
2
In practice you cannot get zero resistance in the cells, though you could use superconductors to get zero resistance in the connectors.
If the theoretical situation where there is zero resistance in the cells and in the connections between them, then applying Ohm's Law to the circuit loop containing the cells shows that either the cells have the same EMF or ...
2
Each alternating current electrical device is designed for a certain power requirement. Because the device is running off of alternating current, there is more involved than Ohm's Law. Resistance for alternating current comes from "classical" resistance, and from inductance, whereby the alternating magnetic field of an inductor resists changes in ...
2
A lamp will light up if there is a potential difference across it. The current can flow through the middle diode, so the potential in the top horizontal wire is the same as in the bottom horizontal wire, so the potential across lamp 2 and lamp 3 are both zero. The potential across lamp 1 is just the potential of the battery so it lights up.
EDIT: This ...
Only top voted, non community-wiki answers of a minimum length are eligible
