Why does a loose electrical connection cause heat?

Question

I know that the more current that flows the hotter something will get, but a loose connection would generate more resistance thus limiting current flow. So why would a loose connection generate heat if there is now less current flowing?

Answer 1

A loose electrical connection has more resistance.

Current flowing through the poor connection causes a voltage drop across the connection.

Voltage Drop = Current x Resistance

Voltage Drop x Current = Watts

Current x Resistance x Current = Watts

I²R = Watts

Answer 2

Loose Electrical Connections

Answer 3

Your logic about resistance limiting current is correct if dealing with fixed resistances/impeadances of the entire circuit. The current flow would be reduced as total resistance of the circuit increases and the load would see a drop in voltage.

However in some circuits such as a motor under load the reduction of voltage actually causes an increase in current. Consider the motor is doing the same work and draws the same power.( increase voltage results in a decrease in current OR decrease the voltage results in an increase in current.)

So a loose connection causes a reduction in voltage at the motor which causes the motor to draw more current. Since power equals (Current x Current) x Resistance (P=I^2R)

Now lets consider a fixed resistance 100 ohms @ 100 Volts draws 1 amp and has 100 Watts of power.

Your loose connection of say 2 Ohms is added to the circuit
102 Ohms (total resistance) at 100 Volts = .,980 Amps

Edit:
You are correct the current did drop and the total Voltage for the entire circuit is still the same 100V but instead we have :
102Ohms x .98Amps =100 Volts
Kirchhoff's law states that in a series circuit the current is the same for all resistances and the voltage divides across the resistances

So your 2 Ohm loose connection has .98A flowing through it

.98 x .98 x 2 = 1.92 Watts
And the 2 Ohms loose connection is dropping almost 2 Volts across the bad connection leaving about 98 Volts for the load.
That is quite a lot of heat on a loose connection which cannot dissipate that quantity of heat. Temperature rises when you can't get rid of the heat fast enough.

Answer 4

In your hypothesis for current flow, you forget the load resistance. A poor connection also means, as has already been pointed out, a higher resistance. Barring a resistance high enough to over come the current demand of the load, the applied voltage will continue to try to supply the load with the current being demanded by it.

Answer 5

A loose connection generates more resistance thus reducing current flow. This resistance disipates a power P=I^2 * R.
Disipation occurs like heat. This is reason for generated heat in a loose connection.

Answer 6

The contacts may not be engaging properly.

The electrical current flows from one contact to the next. When one of the contacts is just barely touching the other, all the current flows through a smaller connection.

Imagine passing a few amps of current through a 12 AWG wire.

Now pass the same amount of current through a 28 AWG (thinner) wire. The thinner wire will be get warmer than the other. Same principal.

Answer 7

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Since the blower motor works properly intermittently, I agree that a bad connection is more likely to blame than a bad blower motor. You need an electrical circuit diagram that shows how the battery wire is connected through the blower motor's speed switch and resistor pack before it connects to the motor. Then the metal motor housing gets grounded to the metal body of the car to complete the circuit path from the battery through the fuse, switch, resistor pack, motor winding to ground and back to the black negative terminal of the battery. One diagnostic technique to use the next time the blower stops working is to jiggle the wires along the electrical path described above to see what connection point causes the motor to run when you yank on the wire a bit or tap on a switch or module etc.

Answer 8

A loosed electrical connection is the cause to increase resistance value (R). But heat is power (P), and current is (I), we have a formula P= R x sprt(I). If good connection we has it's resistance nearly equal zero so P value is very low and it isn't depended to current I. when resistance is increased thus P begin increase too.

Answer 9

because it is arc,.ing. it is sending a charge threw the bad connection and it is hitting oxygen on the way and building the temperature up to overload another component and cause a Major breadown.