4.
已知曲线\(C\):\(y^{2}=4x\),\(M\):\((x-1)^{2}+y^{2}=4(x\geqslant 1)\),直线\(l\)与曲线\(C\)相交于\(A\),\(B\)两点,\(O\)为坐标原点.
\((\)Ⅰ\()\)若\( \overrightarrow{OA}\cdot \overrightarrow{OB}=-4\),求证:直线\(l\)恒过定点,并求出定点坐标;
\((\)Ⅱ\()\)若直线\(l\)与曲线\(M\)相切,求\( \overrightarrow{MA}\cdot \overrightarrow{MB}\)的取值范围.