What Is the Effective Resistance of Headlights in a Car Battery Circuit?

[dblanche]

I can't seem to get this one, I just don't know how to calculate the effective resistance, what is the difference between effective resistance and normal resistance??

Here is the question:


A car battery has a source voltage of 12.00 V and an internal resistance of
0.015 Ω. When the headlights are turned on (while the engine is not running)
the output voltage of the battery drops to 11.75 V. The effective resistance of
the headlights is nearest to:


If someone could just give me a formula or some hints...that would be great!

 

[Andrew Mason]

I can't seem to get this one, I just don't know how to calculate the effective resistance, what is the difference between effective resistance and normal resistance??

Here is the question:


A car battery has a source voltage of 12.00 V and an internal resistance of
0.015 Ω. When the headlights are turned on (while the engine is not running)
the output voltage of the battery drops to 11.75 V. The effective resistance of
the headlights is nearest to:

Think of the battery as a pure source of 12V in series with a .015 Ω resistor. At the current drawn when the headlight is connected, the voltage drop across the resistor is .25V. Work out that current and determine what the resistance of the headlight is.

The effective resistance is the same as the normal resistance.

AM

 

[chai940610]

hello,may i know what the answer?

 

[Andrew Mason]

hello,may i know what the answer?

Welcome to PF. The short answer is NO. You have to try to work it out first.

AM

 

[asteriatic]

Effective resistance is the overall resistance experienced by a circuit or component when multiple resistances are present. In simple terms, it is the equivalent resistance of the entire circuit or component.

In this scenario, the effective resistance of the headlights can be calculated using Ohm's Law: R = V/I, where R is the resistance, V is the voltage, and I is the current. Since we know the source voltage and the drop in output voltage, we can calculate the current using I = (V1-V2)/R, where V1 is the source voltage and V2 is the output voltage. The internal resistance of the battery (0.015 Ω) can also be factored into the calculation.

Once you have calculated the current, you can use it in the formula R = V/I to find the effective resistance of the headlights. Keep in mind that this will be an approximate value, as there may be other resistances in the circuit that are not accounted for. However, this will give you a good estimate of the effective resistance of the headlights in this particular scenario.

It is important to note that effective resistance is different from normal resistance in that it takes into account all the resistances in a circuit or component, while normal resistance only considers the resistance of a single component. In other words, effective resistance is a more comprehensive measure of resistance in a circuit.