Hot answers tagged

45

tl;dr Batteries do not create electric fields to move charges. They move charges, which creates electric fields. a battery [...] gives out some electric field that moves through the circuit and gives a force on electrons in conductor to produce current. This description is, if not completely wrong, at least misleading. A battery is not a source of electric ...


30

Think of a battery as an escalator (potential gravitational energy and potential electric energy/voltage are analogous here). If you have two escalators side by side, taking either one will get you to the same height. If you have two escalators in a row, you will have to take them both and therefore get twice as high. The advantage of escalators side by side ...


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 ...


16

Since you seem to be eager for an analogy-free answer, I'll try to give it a stab. I think this question is actually a bit deeper than some of the answers are giving it credit for, and so far I think trentcl answers your question the best: the root cause of your confusion is that you are assuming that batteries act as sources of fixed fields, rather than ...


11

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 ...


6

If a battery is defined as a device that maintains a constant voltage across its ends, then automatically the problem is solved. When connected in series each battery maintains that constant voltage across its ends and hence they add up. But If connected in parallel, they remain the same by definition. But this is not an answer unless I explain why the ...


6

This is dealt with in the field of electrochemistry. Here is a simplified explanation: Chemical reactions involve the outermost electrons of the reactant atoms and some of those reactions can be modeled as one atom "giving" an electron to another. There are certain types of such chemical reactions in which the electron can be captured and diverted ...


5

Think of this in the water analogy. Wires are represented by canals, the height of the water level is the voltage and the flow rate is the current. A battery, by definition, raises the voltage on one of its terminals by a set amount compared to its other terminal. So in the water analogy it's like a pump that keeps the water level on one end 2 meters higher ...


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

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

OK, there are a lot of answers here, but they're all long, I don't really like any of them, and the answer is simple, so here's another one... All by itself in space, a battery will push electrons from its positive terminal to its negative terminal. This will create a field such that moving an electron along any path from its positive to its negative ...


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

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

... 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

From one of your comments I read In my second statement I am asking why do always the plates of capacitor gets an equal and opposite charge no matter how we connect it in any circuit Allow me to show that this is in general (and in general I mean not in a circuit) not the case. The isolated capacitor The plates of an isolated capacitor can host different ...


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

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

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

Each electron is individually pulled (randomly?) from the lower potential terminal (negative terminal of the anode) of one of the two batteries and works its way through the load device to ultimately return to the higher potential terminal (positive terminal of the cathode) of the same battery. (The positive and negative signs of the terminals refer to ...


2

Yes, the current depends on the internal resistance. And that resistance has been adjusted to give a current that corresponds to 11 W. (By the way, note that we typically don't symbolise the wattage, the power, with $W$ but rather with $P$.)


2

Yes. Your reasoning is correct. You can simply add the potentials as Maxwell's equations are linear.


2

I wouldn't say so, no. Firstly, the key difference between a capacitor and a typical battery is the state in which the energy is stored. A capacitor is the only device that can be said to store "electricity", meaning what is being stored is the actual charges and charge separation on two plates. In a battery, the energy content is stored ...


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