The question is a bit ambiguous. It could mean two different things:
- If the "light source" is powered by a voltage and current, how does changing that light source affect the voltage and current powering it?
- If the "light source" illuminates a circuit with a photosensitive component (like a photocell), how does changing the light source affect the voltage and current in that circuit?
We'll address both interpretations.
Scenario 1: Changing a Light Bulb (Load) in a Circuit
This is the most likely interpretation. Here we're considering a circuit where a light bulb is connected to a power supply (constant voltage or constant current). Changing the light bulb changes the load on the circuit.
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Constant Voltage Source: If the power source provides a constant voltage (like a wall outlet), changing the light source (e.g., replacing a 60W incandescent with a 100W incandescent) will change the current drawn. A higher wattage bulb requires more power, which translates to a higher current draw. Ohm's Law (V = IR) explains this: if voltage (V) is constant, increasing resistance (R, generally lower for higher wattage bulbs) will decrease current (I), but more complex behavior may be observed as the resistance of a light bulb will increase with the temperature. A burnt out light bulb presents essentially infinite resistance, thus zero current will flow. Conversely, if the light bulb has very low resistance (say, a short circuit), a very large current will flow.
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Constant Current Source: If the power source provides a constant current (less common for household lighting, but possible in some specialized lighting applications), changing the light source will change the voltage across the light source. A higher resistance light bulb will require a higher voltage to maintain the same current. A burnt out light bulb presents essentially infinite resistance, thus the voltage will rise as high as the current source can provide to maintain the set current.
It's important to note that incandescent light bulbs have a positive temperature coefficient of resistance. As they heat up, their resistance increases. Therefore, the relationship between voltage and current is not strictly linear, especially for incandescent bulbs.
Scenario 2: Changing a Light Source Illuminating a Photosensitive Circuit
This scenario involves a circuit containing a photosensitive component, such as a photocell (photoresistor or photovoltaic cell). The light source illuminates this component, affecting its resistance or generating a voltage/current.
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Photoresistor (Light-Dependent Resistor - LDR): An LDR's resistance decreases as the light intensity increases.
- Increased Light Intensity (e.g., brighter bulb): The LDR's resistance decreases, leading to a higher current flow in the circuit (if voltage is constant) and a lower voltage drop across the LDR (if current is constant).
- Decreased Light Intensity (e.g., dimmer bulb): The LDR's resistance increases, leading to a lower current flow in the circuit (if voltage is constant) and a higher voltage drop across the LDR (if current is constant).
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Photovoltaic Cell (Solar Cell): A photovoltaic cell generates voltage and current when exposed to light.
- Increased Light Intensity (e.g., brighter bulb): The photovoltaic cell generates a higher voltage and a higher current.
- Decreased Light Intensity (e.g., dimmer bulb): The photovoltaic cell generates a lower voltage and a lower current. The relationship between light intensity and voltage/current generation isn't linear; it's more complex and depends on the cell's characteristics and operating conditions. Also, the wavelength of light affects the performance of photovoltaic cells; different wavelengths of light affect them differently.
Summary
Changing a light source's impact on voltage and current depends entirely on the context: whether the light source is the load in a circuit, or whether it illuminates a photosensitive component in a circuit. In the first case, the bulb characteristics determine changes in current (constant voltage source) or voltage (constant current source). In the second case, the type of photosensitive component (LDR or photovoltaic cell) dictates the voltage and current changes based on light intensity.
