Final answer:
The current from a battery is direct current (DC) and flows in one direction, while the current from an electric socket is alternating current (AC) and periodically reverses direction. A battery's voltage is constant, but the amount of current varies with the load, and for AC, both voltage and current vary over time.
Step-by-step explanation:
The difference between the current from a battery and the current from an electric socket lies primarily in their type and characteristics. Current from a battery is direct current (DC), meaning it flows unidirectionally from the positive to the negative terminal. It is the steady state of a constant-voltage circuit. Meanwhile, the current one typically gets from an electric socket is alternating current (AC), which changes direction periodically, often sinusoidally. AC is used for most household appliances and commercial applications, as it can be easily transformed to different voltages and is more efficient for long-distance power transmission.
Electromotive force (emf) is related to the potential difference provided by a power source like a battery and is measured when there is no current flow. The terminal potential difference is what's actually across the battery terminals when it is connected in a circuit, and this can be less than the emf due to internal resistance. While the voltage output of batteries and AC sources can both be measured in volts (V), the amount of current they supply can vary based on what is connected in the circuit, and in the case of AC, it also varies in time.