# Tag Info

-1

its very simple, follow these steps 1)as the circuit tends to infinity, consider the equivalent resistance to be R(e) 2)consider the parallel resistors i.e., BC and the rest to the right of BC. these are in series with AB 3)now the total resistance to the right of BC will be equal to the effective resistance of the total circuit R(e), as the circuit tends ...

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Because when you take the sine of 0º to 360º and plot the graph of these values, AC current behaves the same way. It can also be represented by a cosine function, but in this case we assume that the initial value of the AC current shouldn't be zero.

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Hint in a parallel circuit, the voltage across each resistor is the same. What is the voltage across the $4 \Omega$ resistor?

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Reluctance = $\dfrac{l_e}{\mu A_e}$ where..... mu is the absolute permeability of the material, $\mu_0 \mu_r$ $l_e$ is the circumference of a circle at a radius r and $A_e$ is a small cross sectional area. The circle I refer to only relates to the cross section of the torus and r is the radius from the centre (where the wire is). All these reluctances ...

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I think the shaking action causes the batteries to move slightly, thus 'scraping' the contact area on the batteries and the contact elements in the remote. This improves the conductivity, and so on. Certainly I've had success opening the battery compartment and physically rotating the batteries and/or scraping the contacts gently. I think it's unlikely ...

3

Batteries contain various liquids that are important for the voltage to be produced. Sometimes, the liquid – even water – may turn to gas and it is permanently lost, along with the capacity. Sometimes, the liquid just moves to one side of the battery which is also bad. Shaking a weak battery may homogenize the concentration of the liquid across the battery. ...

0

As you stated, we can think of a real battery as an ideal one with an internal resistance $R_i$. This battery is then connected to an external circuit with resistance $R$. Those 2 resistors form a voltage divider. If the EMF has a value of $V$ then the voltage measured across the external resistance is $V*R/(R+R_i)$. This voltage is equal to the EMF of the ...

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When we derive Ohm's Law using the Drude Model, we assume at one point of time that E=V/L, when is fact, E=dV/dL, unless E is constant, in which case the assumption E=V/L is true. But I don't understand why the electric field in a conductor must be constant as current flows. Generally, the electric field in a conductor does not have to be constant (in ...

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An easy way to prove Ohm's law for electric fields that aren't constant is to first assume that the electric field is approximately constant over short lengths, just like $E=dV/dL$ suggests. Using that, you can derive Ohm's law for short lengths of material, $dV=IdR$. We'll assume that "current in = current out", which is true at steady-state. This allows us ...

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The current $I$ has a value in one point of the circuit, in contrast to the voltage $U$ which is always measured between 2 points. The definition of $I$ is the amount of charge $\Delta q$ that passes through a particular point in the circuit in the time $\Delta t$ (it's a quantity mathematically similar to the simple velocity in kinematics). So when you ...

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What is voltage? The way I see it, and this is only my concept, voltage represents electron pressure. because electrons repel each other,the more electrons you pack into a unit mass of a conductor the higher the voltage, such as in a metal foil capacitor. If you force electrons onto a non conductor, the room for electrons is very limited and the static ...

2

Two capacitors in parallel have the same voltage. Two capacitors in series have the same charge. Simplify the problem to two capacitors in series (each started life as two capacitors in parallel) - what is the ratio of their voltages. Then use $Q=CV$ to figure the charge on each pair; finally distribute the charge on the elements of each pair according to ...

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Assuming for now that this is homework, I'll provide this hint: the voltage on the 8.73 $\mu$C capacitor is not 21.9 V. Don't forget that that voltage has to be distributed among all of the components.

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In principle, it is possible, using, e.g., high-current relativistic electron beams - please see, e.g., the review http://arxiv.org/abs/physics/0409157 . @John Rennie offers reasonable arguments, but the very real problems he mentions can be overcome - I don't have time to describe the specific mechanisms (see the review). In experiments, propagation length ...

2

The cathode ray tube has had the air pumped out. Electrons scatter off oxygen and nitrogen molecules so if you fired an electron beam in air it would be scattered in a short distance. The distance would depend on the beam energy, but it's a lot shorter than 100m. The range of electrons from beta radiation in air is around a metre. You could argue that ...

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To start with one could have an ac current never grounded anywhere , for a household generator for example. The reason one grounds at the generator is for safety so the ground can pick up any miss chance, as it is a practically infinite sink for electrons. Only one of the two lines can be grounded of course :). It was found though that due to capacitences ...

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There is a LOT of capacitive coupling between the neutral wire and ground even if a DC current cannot flow. And we are talking about AC here.

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In my opinion the contribution of hysteresis losses in an iron wire can be important when comparing with conductive losses, but this is an issue strongly dependent of the iron alloy used according to hysteresis loop, conductivity and permeability. The analysis of the induced current distribution in conducting wires subjected to a harmonic axial voltage is ...

2

There is a commonly used analogy for electric circuits called the hydraulic analogy. This imagines the electrons as water and the wires as pipes. The voltage is equivalent to the water pressure and the current is equivalent to the water flow rate. Start with a DC current and imagine the water is doing work by flowing through a water wheel: This is all ...

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At a beach the waves carry energy and momentum from the sea to the shore, even though the water in the waves moves back and forth. It is the same way with alternating current: what matters is the energy flow carried by the electric and magnetic fields, not the movements of the charges.

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If the voltage reverses doesn't the flow of electrons reverse? It depends. If the alternating voltage is across a diode then, no, the current through the diode doesn't (effectively) reverse but is instead unidirectional. However, a genuine alternating current periodically reverses direction - the electric charge 'sloshes' back and forth within the ...

-2

A metallic wire is electostaticly neutral the mobile negative charges equals the strongly Bounded pisitive charges , so resultant electric field is zero everywhere.

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