Final answer:
The relationship between current and resistance is such that if all other factors are held constant, an increase in current typically indicates a decrease in resistance. However, without context, resistance cannot be directly determined from current change. The resistance of a circuit decreases when resistors are added in parallel, and the resistance of a bulb can be calculated using Ohm's law.
Step-by-step explanation:
If the current goes up in a circuit, the resistance can either go up, go down, or remain the same depending on other factors in the circuit. In Ohm's law, current is inversely proportional to resistance, meaning if all other factors remain constant and the resistance increases, the current would decrease, and vice versa. However, if the current increases without adjustments to voltage, this may be due to a decrease in resistance, assuming ohmic conditions. Therefore, without additional context, the resistance cannot be definitively determined with just the information that the current has increased, leading to answer 4) Resistance cannot be determined.
When resistors are added in parallel, the total resistance of the circuit decreases because parallel resistors provide additional paths for the current to flow. If two identical resistors are connected in parallel and the resistance of one is increased, the current through the unaffected resistor remains the same, and the voltage across it also remains unchanged, maintaining the steady state and leading to answer a) The current and the voltage remain the same.
The resistance of a bulb with a current of 1.25 A and a voltage supply of 4 V can be calculated using Ohm's law as V = IR, which gives us R = V/I. Thus, the resistance would be 4 V / 1.25 A = 3.2 ohms. If the voltage supply is increased to 7 V, the new current can be found using the same formula: I = V/R, which would give us 7 V / 3.2 ohms = 2.1875 A, assuming the bulb behaves as an ohmic resistor.