#resImage_250 {
    display:block;
    overflow:hidden;
    background-image:url('https://www.tjelectrical.co.uk/assets/images/9/electrical-contractors-302f6460.jpg');
    background-repeat:no-repeat;
    background-position:center center;
        width:100%;
    background-size: cover;
        height:450px;
}
@media screen and (min-width:700px){
    #resImage_250 {
        background-image:url('https://www.tjelectrical.co.uk/assets/images/2/electrical-contractors-1aea6964.jpg');
                height:375px;
    }
}
@media screen and (min-width:980px){
    #resImage_250 {
        background-image:url('https://www.tjelectrical.co.uk/assets/images/3/electrical-contractors-6daa837f.jpg');
                height:470px;
    }
}
@media screen and (min-width:1400px){
    #resImage_250 {
        background-image:url('https://www.tjelectrical.co.uk/assets/images/3/electrical-contractors-6daa837f.jpg');
                height:470px;
    }
}