Fill in the following blanks with suitable words: a) The lines of ….. round a straight current-carrying conductor are in the shape of ….. b) For a current-carrying solenoid, the magnetic field is like that of a …….. c) The magnetic effect of a coil can be increased by increasing the number of ………, increasing the , or inserting an …. core. d) If a coil is viewed from one end and the current flows in an anticlockwise direction, then this end is a pole. If a coil is viewed from one end, and the current flows in a clockwise direction, then this end is a …..