why does the cord present in the electric heater nt glow while the heating element does?

Question

please help me!!!!!!!!!!!!!!!!!!!!!!!!!!

Answer 1

It is because the heating element has much more resistance than the cord. The current flows easily through the cord, but then backs up when it enters the heater coil. This electrical friction produces heat. Electrical engineers measure the resistance of the cord and the heater and then calculate the amount of heat which will be generated when ordinary house current is run through the system.

Answer 2

Here's a simple way to see this ... and to correct the mistake in one of the other answers.

Power = Voltage x Current

and

Current = Voltage / Resistance

So

Power = (Voltage) (Voltage) / Resistance

if we have a 1200 watt heater, connected to 120 volt supply, that means the Resistance in the heating coil is 12 ohms

1200 = (120) (120) / 12


A copper wire, as mentioned in some other answers, will have a resistance in the hundredths of ohms, or lower. The resistance is related to the size of the wire, and for ordinary power cords is extremely low. So, the circuit is actually three resistors in series: the wire to the heating element to the wire back to the power source from the heating element.

Suppose the wire had a resistance of 0.01 ohms, and the heating element has a resistance of 12 ohms. The total resistance in the circuit is

R = 0.01 + 12 + 0.01 == 12.02 ohms

The current in the circuit is

I = V / R , so 120/12.02 = 9.98 amps approximately

The voltage drop across each of the circuit elements in this series circuit is

V = I * R,

so, for the wire segments, each has a voltage drop of

9.98 * 0.01 == 0.01 volts (approximately)

so the power dissipated by each of the wire segments is

P = V * V / R = 0.01 * 0.01 / 0.01 == 1 watt approximately

For the heating element, the voltage drop is

V = I * R = 9.98 * 12 = 119.8 volts

and the power dissipated by the heating element is

P = 119.98 * 119.98 / 12 = 1199.6 watts

So the wires will not even be warm (even with 0.01 ohms, which is higher than they are actually going to be), while the heating element will be 'toasty' giving off about 1200 watts.

Answer 3

The power cord is much lower resistance than the heater element (heater elements are usually made of an iron compound that has several times the resistance for the same cross-section per length as copper power cords).

For example, a 1200 watt, 120 volt heater will have an element of 0.1 ohms resistance, but the power cord might have only 0.001 ohms resistance. Therefore the power cord will only burn 1/1000 of the power that the element will burn, as in 1.2 watts, not enough to heat it up very much.

Answer 4

Different resistance. The line cord is made out of copper wire of adequate size so as to provide a low resistance. The heating coils are made out of a more resistive material (usually an alloy called Nichrome) which generates much more heat as a result.

Answer 5

It is because of the resistance in the conductor. The higher the resistance the more it will heat,but if the resistance gets too high there will not be enough current to heat the conductor.

Answer 6

You'd better hope it stays that way!

That's the way it's designed. If the cord starts to glow, grab a fire extinguisher...