The number of turns of cable in a coil has a direct effect on the voltage induced due to Faraday's law of induction. When the external magnetic flux changes, it induces a voltage in the conductor, such as a cable. By winding the cable into a coil, the field lines intersect the circuit multiple times, thus increasing the induced voltage. When building a coil, it is important to consider the number of turns on each reel.
A large resistor will decrease the current if the power supply is not changed. However, if you first build the coil and then choose the voltage of the power supply, you can achieve whatever current you want. Therefore, it is important to focus on the coil and projectile first and then choose an electrical source that can provide both the voltage and current needed. Additionally, select power output transistors that can manage their voltage, current and power.
This rule is why thick coils are often used in reel guns. It can add twists more easily than a larger power supply can. The whole exercise of designing a helical cannon consists of placing the projectile close to the coil so that the system seeks the minimum energy state. This occurs when the projectile is in the center of the coil and requires pouring a lot of mechanical energy into the projectile for everything to reach that state.
If too much energy is used, however, the coil may not be able to dissipate heat fast enough and may melt with a single shot. For this reason, thicker cables are better for large motors. To supply huge current cheaply, large capacitors or car batteries may be used. However, there are limits to their physical dimensions and capacitance as well as their WVDC rating (working voltage dc).
In addition to this, an experiment was conducted with secondary coils having only five or six turns and joined together by two nails at their tips. The EMF induced in a coil is equal to the negative of the rate of change of magnetic flux multiplied by the number of turns in the coil. Voltage is applied to the primary coil which produces a changing magnetic field in an iron core. A transformer consists of two coils: primary and secondary coils wound on a soft iron core.
Any change in its magnetic environment will cause a voltage (EMF) to be induced in it. This could occur by changing intensity of magnetic field, moving magnet towards or away from coil, moving coil into or out of magnetic field, rotating coil in relation to magnet etc. In one experiment, when magnet moved towards coil, galvanometer deflected left in response to increase in field. This led to such high current that tips of nails melted. In another experiment, researcher had an article on optimization of condenser-actuated helical gun in IEEE Transactions on Magnetics.
