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Current is the measure of the actual number of electrons traveling per second. I'll make an analogy to water flowing through a pipe to give you a better idea. Voltage is water pressure. It pushes the current through the wire. Current is the actual water. More current means we have a greater flow rate, more water is flowing through the pipe. We need lots of pressure to send the water a great distance, this is why transmission lines typical have voltages of 10 kV or higher. We need lots of flowwing water to power, say a paddle wheel. But we need both. If we have a million gallons sitting in a pipe yet no pressure to push the water through, the system is useless. Voltage and amperage are equally important.
creates a magnetic field around the conductor. Creates heat as it travels through conductors that always have some resistance.
If the circuit is closed, then the current flows in that circuit. Due to this small magnetic field will be created near the conductor through which current is flowing.
And finally when it travels through the load, be it a motor, light bulb, or any device that is designed for the amount of current it creates heat, light, mechanical rotation etc.
When someone says that's there is current in the circuit ,its actually means charge is flowing in the circuit (electron in case of conductor)these charge with them carries energy field up by battery or some other source .which is then use by electrical appliances connected in circuit .Lets take the case of bulb which use this energy (carried by electron) to give light and some part is converted in to thermal energy in form of heat that's why bulbs are hot when light up for some time and also electron have to pay some part of its energy in moving through wire just like the road tax we pay to ours government .