Why should the resistance wire of the electric furnace be selected with a large resistance? Isn t it

The electric furnace is used in parallel, you are constant, according to i=u r, the greater the resistance, the smaller the current, so the heat obtained by q=uit is smallerThe student also said that the larger the resistance, the greater the heat, the series circuit is right, and the parallel circuit is calculated by dividing the square of the voltage by the resistance. A resistance wire of 10 emits more heat.

Parallel circuit, you constant, the same time. According to q=u 2t r, the lower the resistance, the more heat is emitted.

You can't use Q=UIT to calculate calories, but Q=i 2rt, and you may not be able to understand it here, the answer is 10 ohms.

Work regulations: The work done by the current on a certain section of the circuit is equal to the voltage at both ends of the circuit, the product of the current in the circuit and the energizing time Because w=uit, it is the definition of electrical work So any condition can be used.

We must pay attention to the selection of the appropriate formula for electric work, and the parallel connection is generally used u 2 r t, so the ratio of heat is 1:2

Direct Joule heating can only be found using this formula, or indirectly, for example, an electric motor, using the work of the current - mechanical energy.

Electric work = power * work time = work voltage * work current * work time.

p=ui,w=pt=uit

Electric work = electrical power x time = voltage x current intensity x time.

For w=pt, this is the source system of work and power.

Power indicates how fast or slow work is done, and this formula applies to any relationship between work and power. This celebration.

For w=uit, it indicates how much work is done by the current, and also indicates how much electrical energy is consumed by the electrical appliance.

For an electrical appliance, the amount of electrical energy consumed is directly proportional to the voltage at both ends, the current passing through the mode state and the energizing time. So this formula is true.

U=IR is not suitable for non-pure resistive circuits.

This formula describes the relationship between voltage and current, in fact it only describes the special case in a purely resistive circuit.

There are not only resistors in the circuit, but also inductors and capacitors (of course, you may not have learned), and the relationship between voltage and current is not simply proportional (and inductance and capacitance also have a lot to do with it, for example, for circuits with motors, due to the presence of ** circles in the circuit, this belongs to inductance, and the circuit will show different characteristics from pure resistance circuits).

To explain here, if the circuit is direct, then the action of inductance and capacitance fails, and the circuit is just a purely resistive circuit.

If it is not a pure circuit resistance, for example, the motor is connected to the voltage u, the motor starts to rotate, of course the motor has a resistance r, there is a current i in the circuit, and the current has a voltage drop of u1=r*i in the resistance, but it cannot be written as u=r*i, because when the motor rotates, it also needs electric energy, and a part of the electric energy is the resistance heating q=i2rt, and the other part of the electric energy is converted into the kinetic energy of the motor rotation.

It is not a pure resistance circuit, and the voltage and current do not change proportionally, that is, if it is not a pure resistance circuit in the formula p=ui, the formula cannot be equated, and the result of i rt is the result obtained after a lot of scientific experiments and is applicable to all circuits.

Q refers to the heat generated by the circuit, in addition to the magnetic loss, there is only one device that generates heat in the circuit, which is the equivalent pure resistance. Although inductors and capacitors absorb a lot of current from the voltage, they are not used to generate heat, but only store and release them, while the resistors absorb the voltage and current and radiate them in the form of heat. Because Q refers to the heat dissipation on the pure resistance, Q=IIR, is his definition, just like the essential definition of power P is UI, but in the pure resistance circuit U=IR, but in the non-pure resistance circuit U≠IR, U=iz, Z is the impedance of the circuit, the impedance is the pure resistance plus the virtual resistance, the Xu resistor absorbs a lot of power, but does not heat, only the pure resistance will absorb the power to heat, this heat is Q (quanlity of heat).

Only when all the electrical energy is used to generate heat, as for the electrical energy that is not mainly heated, it is not possible!

Q is the meaning of thermal energy, because it is a pure resistance, so the work done by the current is all converted into internal energy and does not contain mechanical energy.

In non-purely resistive circuits, such as electric motors, it is thought that electrical energy is not only converted into thermal energy, but also into kinetic energy. If you use resistance and current substitution, for example, use p=i 2*r to calculate the electrical power, it is not possible, because what you calculate in this formula is the power of the resistance in the motor, and the part converted into kinetic energy cannot be found...

Dynamo? Motor? When the motor is working, the electrical energy is converted into mechanical energy and internal energy.

Is the question you saying wrong?

Because the engine not only has resistance, but also the inductance of the inductance x, x is generally not known to you, you can't calculate.

Because the resistance of the motor does not change, it cannot be used.